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This exercise is actually a kind of wrap up for everything we learn in this section.

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It's actually a very demanding exercise on the goal of it is this you have to find a way to use a combination

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of touches to do a transform on a given object.

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You want to be able to a scale an object using touches as well as a rotating object using touches.

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So if user puts one finger down on one top on the device and moves that that's going to essentially

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rotate an object.

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And if those two types sound you have to be able to scale that object.

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Or let's call it a UI view.

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For instance there is and I said it's a demanding exercise is simply because you have to be able to

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find your way around finding how many touches are there and then finding the distance between them.

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If you're going to scale something as well as finding the angle that is being used at any given time

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if there's just one touch Now I know it's a difficult one perhaps and you might want to spend some time

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researching it online but they still suggest that you actually give it a try on your own and try to

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find some references outside before you look out.

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My solution for this exercise really help you in any situation that comes to using C.G. transform.

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And the combination of touches.

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And of course you could do all of these simply by using gestures but they want to make sure that you

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get a sense of everything that touches they do for us as well.

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So I'm going to pause the video for a few seconds that you can pause it now and get it started.

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And once you have done it hopefully or if you want to look at my solution you can resume the play by

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OK.

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This code works code and I'm going to start a new project.

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Then I call it transform it.

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Touch

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and in my transform with Tadhg I'm actually going to do everything in the programming side so I don't

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need to go back and forth between the Interface Builder and here.

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So in here I'm going to go ahead and say I have a variable let's call it that red box which is of the

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type you I view.

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And then in my view the load I'm going to go ahead and say red box becomes a UI view of a frame that

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is going to be let him auto complete those for me that say 0 0 0 200 and 200.

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And the reason I stick it at 0 0 because it's a it's something I'm really used to.

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Which is what I would want to do this kind of test stuff.

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I just say my main object in this case red box.

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It becomes at the center of the scene.

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So it gets a red box that sento self that you that center.

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So you put it wherever you like it.

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And then we center it against against the view and then self-taught if you add the sup you read you

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or a box and then the red box the background color becomes a color dot right.

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I'm also going to add one more thing which really you don't have to for you I use.

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Just in case some of us have forgotten and I'm going to say red box start user interaction enabled is

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true.

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So it makes sure that this object is user interactive and if you run the application by now we should

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see a red box of the size 200 and 200 somewhere in the middle of our our simulator which is exactly

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what we expect it to be.

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That's that.

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So now the important thing we want to do next is finding the two ways that this thing will be manipulated.

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So I'm going to say such as move it because that's what I care about.

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And then the touch has moved I'm going to have two distinct situations.

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One is if one touches that counts was the one.

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So in this situation I'm going to write it rotate and then I'm going to have another one else if touches

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that the count was two and then I'm going to say the OK.

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So if there's only one touchdown.

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When I wrote it.

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If the two touches down we want to escape now in both of these I'm going to get my touches so I'm going

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to say touches one then let's say let's touch one or might touch one or touch one is better then obviously

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it becomes a touch as does the first.

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That's the simpler one because simply we know there's only one touch.

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Now if there are more torture's because this is a set we can't just get the touches from it we have

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to actually either iterate through all the touches or we have to convert all stages into an array of

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touches which is what I'm gonna do.

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And when I say let's touch as array for instance that becomes an array of touches.

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So we get all of our touches on we place them inside an array.

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And since now they are in an array we can get them by number essentially.

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So I could say touch one.

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I actually don't like the naming that has numeric values and it was kind of contemplating in my head

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I'm going to call it touch of one so down that I have that I'm going to say here touch one becomes touches

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Ray and that become the zero object of it.

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And then I have touch too which becomes the first object or an object as a location one.

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So Dawan that part is taken care of.

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Now the important thing and the next important thing that you have to do is you have to make sure that

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in most of these situations things only happen if we are touching the red box or the red the view or

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the red box.

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So yes I'm going to say you touch one dot view is not red box then let's do this let's return.

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You don't have to continue on anymore.

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So if there was only one touchdown but that one touch of wasn't on the red box don't need to do anything.

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I'm actually going to do the same thing in here.

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What in the in the scale.

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Because the two touches I have to say touch one and touch two.

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If both on not on the red box then returned.

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So that really takes care of a big chunk of the problem.

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It makes sure that we only do things if we are absolutely on the on the red box.

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Now is also giving us an error I think is because of the optional thing.

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Yes because our touch has a rate is not an option.

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So we don't have to have the question mark for the touches.

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The Post absolutely do exist.

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So that wasn't taken care of.

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Now it becomes about actually doing the rotation or a scale.

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In this case during the rotation if there was only one touch and in this case doing this scale if there

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was two touches essentially reformat things a little bit so I know what I'm typing because it's going

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to become a longer code.

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So I want to make sure that you know I have it easier for you guys to view.

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So the view of the is taking care of the touches are taken just now the next thing is you have to actually

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calculate the values for the rotation and for a scale.

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I'm going to go ahead and deal with the rotation first and for that I'm going to write a new function

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and then say function let's call it one rotate action and then rotate the action is going to do.

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This is going to get two values in one of them being the touch that we landed and the other one being

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the view that you want to rotate and then it's going to give us a value.

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Not before I tell you what all those input arguments and what's the value you want to get back.

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Let's have a quick look at how this is going to be processed.

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So imagine your user taps on this location which is the last point and then pushes down the finger or

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the top goes down.

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And then you get to the end point.

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And that team is out for that angle is the one that we want to calculate.

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So the difference between the angle between the start point and the center of the main view compared

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to the angle of the end and the center of the main view.

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That's what you want to calculate.

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Now here's the thing there's a little bit of mathematics involved and I don't expect you guys to know

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it or if you are like me you would just go online and Google it and that's what I did.

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I'll try to find out.

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How do you calculate the angle between two points.

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And it turns out the arctangent move is a very good formula for it like there was actually the first

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head showed me there's an arctangent 2 and there's my discussions on a stack overflow that you can read

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them again.

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You're not supposed to know these things is just another off.

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Once you once you reach a place that you need to find it you should be able to go online and find the

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answers if you ask me to calculate the distance between these two or the rotation between them.

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I would definitely want to be able to do it now with that in mind.

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This goes back to school and save for a rotation.

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I want to have the torch that is going to essentially give me the values of the locations.

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I also want to have a view which is the UI view that is our main view or the view that we want to compare

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against.

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And once that is done I want to get a C.G. float.

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I want to get the amount of rotation.

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Now here there's going to be a little bit of a code but most of it is actually very simple on the part

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that is a little bit difficult which is that mathematical side of it we just get it from some online

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resource.

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So the first thing I'm going to say let's kind of point wishes the current location of the top that

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would be touch dot location in view and the view is this input.

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So this is the current location at any point.

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So I'm going to go ahead and say if that's the case thing give me the previous point that's going to

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be touch dart previous location in view the same.

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So essentially if you were to translate it here this would be the very first one previous location.

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This is the kind location.

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Of course it doesn't happen like this.

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It doesn't have such a big jump.

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It is being collected in every drop count.

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But for now we can assume this is kind of an illustration of it.

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So we get these two points was we got the two points.

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I also want to get the center of the view so I'm going to say let's center to be view data center.

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So I'm going to get the center of this view and the reason I gather this one is even though this is

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going to be self cut view I want you to have it in case you want it to rotate against a different center

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essentially.

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So with that I'm going to go ahead and say let current why this is the Quine's location of X or Y doesn't

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matter.

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Y is going to be center dot y minus the point that y.

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So that's the light.

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So I'm going to copy and paste that make it current X is going to be X and X.

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So what these two values show for us is essentially dislocation dislocation devoir x and y are feet

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compared to the center is in my screen right now those values for instance.

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So that's what these two values represent for us.

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And since we have the current ones we also have to get the previous ones.

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I was going to say give me previous y to B and previous Y to be.

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And those are the same thing as before.

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Previous point and previous ones.

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So we find that wherever we used to be and whatever we are now.

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So the next thing is finding the actual angle between these two at any given point.

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So I'm going to say let client angle be arctangent to all the current Y and current x.

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So there's a formula that essentially gets you the angle of any point against the center of the view.

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And then I want to get the same thing for just a socket or B she's going to be the previous angle.

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So the previous one is going to be previous Y and previous x.

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Now again I'm going to have to emphasize on this that the mathematical part of this is not a is not

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the goal of this lesson.

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Essentially this is a formula you can simply find it anywhere online.

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But for us we found the contango we found the previous Nanga.

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So what we have to do is we have to say return anger minus previous Sinar.

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So we have to get what has changed because the new one.

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Verby before return.

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The difference between these two.

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And that's exactly what we needed because we needed to have a CGI float that is the rotation that we

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have.

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So now that you have that let's go ahead and use it in our teachers.

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You know touches off if there was only one touch fish we have to rotate.

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I'm going to go ahead and say let.

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New rotation.

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And maybe the whole thing would become rotate action for each one between self.

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You remember I said that since we are using so that we could simply use it in here.

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But I wanted it to be a separate value about so if we can actually make sure that you could use it for

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other things as well.

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And he's giving you a warning about touch one being on wrapped or not.

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I mean aren't up this actually.

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So this is the new rotation that gets calculated every time the touch moves.

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Now we have to use it to actually rotate the red box.

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So I'm going to say Redbox thought transform becomes Redbox that transform that rotated by their value

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you know new rotation.

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So the value of the new rotation is going to be the amount of rotation that we want to rotate the Redbox.

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Ok then so a lot of call with the let's see what you have done I'm going to run the app to make sure

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that we haven't done something terribly wrong.

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I know something is coming up and I have to explain to you guys but let's see the rotation first and

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I rotate.

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It rotates perfectly.

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So when I tap someone on the red one it rotates based on the movement of my mouse at the moment or a

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tap on the actual device.

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If I touch outside nothing happens.

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Now the next thing we have that I get is the escape.

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And look what happens when I try to escape now which we haven't really done a scale part than I type.

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It is still rotates even though it has two taps down on the device.

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It actually is still thinks there is only one rotates the object.

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And the reason for that is there is something called multiple touch and the multiple touch is not enabled

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yet.

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So here in the view that lot I'm going to go ahead and say the red box doth multiple touch enabled.

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True.

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So for you my view is user interaction is by default.

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True but multiple times is not for most other outlets such as you or I.

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You make you view even the user interaction is not by default enabled.

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So what about your neighbors.

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And if you read on it now.

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Now when I do two taps nothing happens.

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So even I try to do with the toothaches it knows that if you are here and obviously nothing is going

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to nothing is going to happen.

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So that's where we have to.

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What we have to do now we have to find a way to scale this object and scaling is actually going to be

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a lot of code.

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But the good news is is actually going to be a lot easier than the rotation.

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So use that function I want to use for a scale.

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This was the route that I can go ahead and say function.

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And this one is going to be on a scale action and for a scale like shit I need to give parameters all

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three inputs values one of them is the first touch.

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So I'm going to say Tyche let's call it impotent.

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One input Tajh because the other ones are called Touch one and was well.

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So that's going to be a touch and that I have input touch to.

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And I have a name put to view which is going to be the UI view.

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And then at the end we come back with a CGI float.

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The amount of a scale like that actually a stack them so it's a little bit easier to read everything.

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So that's about that.

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So we have to touch as I should have had that.

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Here we have the two touches and we have the view that we want to calculate the scale against.

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So with that this go ahead and get a few things in here.

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First of all I need to find the current location of the torch one and current location of touch to and

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the previous location of touch 1 and previous location of the arch.

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So a lot of our stuff.

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So a lot of let's call it the one that becomes input.

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Touch one dot location in view and that's going to be an input value.

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So let's first get the current location of touch 1 and I'm going to say Get me the second one touch

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to.

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And that becomes touch to perfect.

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Now let's go ahead and get the previous locations and for this also I have a little and illustration

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I can show you.

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And the illustration is this one.

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Imagine this is the starting point the top one and top two and these are the kinds of points type 1

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and top two.

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So the rotation is kind of irrelevant in this example.

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It's just an out of the distance between the two taps at the beginning which becomes the previous locations

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and the current ones I have named them be the start.

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And so tap one and top two and end up one on top two.

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So we have to find their complications as well as their previous locations.

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I'm going to go in here and say give me these two coffee then I'm going to call them previous location

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1 pre location 1 and that's going to be previous location.

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Perfect.

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And when I replaced that there and that becomes pretty as well.

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So by now we have managed to get that complication of touch 1 and previous location of such fun as well

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as the same for type 2.

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The other thing we have to do is we have to now get that distance between chose 1 and 2 in the past

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and the distance between the touches 1 and 2 in the current time.

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So we have to kind of get that distance between them to get to the stands.

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I'm actually going to write a different function.

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Going write it down here so we can kind of see everything together at the same time.

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So yes I'm going to go ahead and say Give me a function called this sounds action friend stance and

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the distance action essentially gets two points.

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So I'm going to say points 1 or input points.

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One important points one that's going to be a C.G. point and input point two and that's going to be

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a CGU point as well.

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Either it has a CD flossed so it gets two locations and gets me the distance between those two.

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So know I'm going to say rather this dance this is going to be a CGI float.

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And I have to make it up on and off it then I'm going to say the calculation between the distance it

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needs a firm.

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This is a much simpler formula and if you remember it from any time in high school it's essentially

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the square root of the square of the difference between the excess plus squared off the difference between

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the winds and the very quake you know search online can get you down.

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So that's essentially the point A and Point B and the distance between get access under ROIs and the

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square root of that it gets you by the distance between them.

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So that's what I'm going to write so I'm going to go in and say let's let's call it X def right.

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That's going to be I have to get the point.

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One input point one dot X minus input point to aim point who Dauth x.

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That's the difference between the axis.

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Let's go ahead and get Devoy difference.

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So that's going to be input difference between the VI and voice.

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So essentially So far we have managed to get that little part inside the Panthers and this one inside

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the two parties.

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So we got the differences between the x and y.

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Then I'm going to say Let x square down would become P or W of X difference to the power of two.

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So that's essentially powering it up.

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And then I'm going to say why Esquith becomes Y difference which is this one the power of two.

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And then the value that are actually interested in is adding these two together and getting a square

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root of it.

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So I'm going to go ahead and say Give me the distance to be this q r t of X A squirt plus y a cyclist.

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So this task becomes the square root of the added value of both of these.

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And then you obviously have to return the distance and the moment I do that we have to this error should

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disappear essentially perfect.

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And now I could go ahead into my scale action the action that's going to calculate these distances for

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me and say let current stance to be dishtowels action between the current distances between the crimes

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locations so collocation one Quine's location off point two.

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And that's going to give me the current distance between them.

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So let's go ahead and duplicate this or let me rewrite it so it's a bit more expensive.

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So I'm worried I'm not going to say let previous this time is going to be this town's action between

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previous location one and previous location.

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And as you can imagine because we're going to get them through the power of two sometime later it doesn't

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matter which is it first which means within seconds.

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It's essentially a distance between them which is always an absolute value.

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It sort of has a positive value.

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So I'm going to go ahead and say well let's let's call this one how to put a scale or a scale ratio

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which is a much better name for it.

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That would essentially become current stars divided by previous distance.

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So this is the value I'm interested in.

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The value of how far they are against each other now compared to before.

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And once we have that value was when I'm going to say a return to scale ratio.

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So that's my scale action and that's perfectly taken care of now.

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So the next thing you have to do is finally essentially using that value in our touch has moved so much

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has moved is here the first touch we have taken off the second touch is the one that you still have

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to do things about it.

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So if you had that I'm going to go ahead and say let's call it let in your new race you're not just

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going to become the name of my action scale auction.

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So your issue is a scale auction between touch one and touch to get even with Team self to view and

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then and then that's it.

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And then calculate the ratio.

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And once you race you I'm going to say Redbox that transformed becomes red box that transformed the

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scale by giving me how much do you want to skate on X and how much on the Y.

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When I say new ratio on.

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So that's about that's that's running this up now.

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And if all works we should have a functioning that rotates and Askins any object or essentially the

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red one for an hour.

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So that's the rotation and that's the scale.

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Perfect.

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So everything is working on that.

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We have very quick clean up of the code and it's a very good exercise and something that I really recommend

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that you guys do it.

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So there's a lot of code in my view control and I want to put them in separate extensions so that I

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say give me a new file.

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This is going to be a swift file of the $0.00 Plus let's call it a scale action so you want to enter

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up there I'm going to say you like shit and I'm going to say this is an extension to view controller.

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And within it we have this scale action.

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So I'm going to cut this fart with it there.

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So the code becomes a lot easier to read because every file in here will have only a limited amount

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of stuff in it.

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I'm going to copy this one because I know it is going to happen again and I'm going to say command and

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you've me on file and this one is going to be a view controller.

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Plus this sounds action.

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This is the one that calculates the distances for us.

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And again it's an extension of view controller and within it we have the distance action going to cut

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that.

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Put it here.

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So that part is taking off.

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Another copy of these commands.

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And swift fine.

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I'm going to call the view controller plus rotate action rotate action and he has a forcefield going

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to put all rotate action which is this one so perfect and if I go back to my view controller I now only

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have the view that lot which are the things that are kind of neat them yeah as well as the touches are

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moved if you wanted.

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You could even push the touches and move somewhere else.

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But I usually keep the kids Mather's VTM the main class declaration but it depends on the complexity

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of what you have.

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If you wanted to you could actually separate them even fair that is essentially an exercise of marginalising

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or partitioning your code which surely simplifies reading the parts of the code to understand.

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A They are very independent pieces which is the core understanding and the core concept of object oriented

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programming and B that you can you can use them separately whenever you need them.

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So that's about that.

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The app is working properly or the way you expected it.

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It's a kind of scale or rotating object.

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A very good exercise in understanding are different things that you could do graphically and using a

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combination of instructions and obviously in the next lesson.