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So far we had a look at some of the delegation that we developed ourselves.

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So we wrote our own protocols.

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We conformed the class to that and then we use that to pass a message.

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Now in this lesson we're going to look at some of the delegations that exist in different classes in

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the U.S. almost every class in the U.S. has at least one delegation and then some of them they have

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a lot more than that.

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So let's have a look at doors in export and what looks good on that to start a new project.

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Iowas application that is actually a good time for us to take what we learned into an actual application

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not a single view of un-Godly.

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That's why if I'm going to say text field the allegations are swift end in here I'm going to go ahead

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and say my a storyboard.

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I have one text that's the only thing that they want to have in here.

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Here's a text that I'm actually going to go ahead to the same thing as usual no borders.

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Make sure the background is something that you can actually view it and that takes a little bit larger

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have a placeholder saying for instance a value line at the site and all of these things and all you

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can do within your own whatever you feel like more comfortable.

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So the next thing is I'm going to have to make an outlet for my text.

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So same thing as before.

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ASSISTANT EDITOR IN MY a class like this one and call it my text file.

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So so far we haven't done anything that is different.

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We have made a text field and get that.

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And now I know one you will know soon as well that most outlets in your interface builder they have

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built in delegates and you can call those delegates by doing either of these two things.

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Either hold the control button and drag them over your view controller in the window that pops you could

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say outlet delegate's which means I'm delegating from my text field to this view controller.

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So let's do that.

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Or you could actually do it through the programming.

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I'm going to do it in both sides so we see both of them.

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So the first one was holding control and dragging over our view controller and saying delegates that's

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one way of doing it.

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I'm actually going to go ahead and disconnect it so I can do it one more way the other way was this

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way I go to my view controller and in my view controller I'm going to clean everything up like usual.

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And in my view that law the moment of you know what I'm going to say my text with that daily guest becomes

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stuff becomes this one.

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Now if you recall anyone that we wanted to assign that delegate to it had to conform to that delegation

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protocol which I'm currently not doing that so I'm going to go to my class viewer controller.

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So for a class you I view controller and I'm going to say you find a text field that delegate's so and

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conforming to you why feel delegate as well.

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So now my view controller can accept delegation methods from my textbook.

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But what are those what are the different functions or properties that we can use from the sky.

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Let's go ahead and google it up.

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I'm going to go to my browser.

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Say Give me your text textfield delegates and go look at the text with delegate and soon enough we will

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learn better ways of finding this matters.

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But for now I'm going to find those.

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I see that in the delegation you know everything is stuff I have textfield should begin editing takes

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with did begin editing.

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So this one gets triggered the moment you start entering a value or it says the one I'm looking for

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actually is something called text which should return.

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Let's read that up and it says Ask the delegate if that takes which should process the processing of

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the return button.

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So weatherman we had ridden by then something should happen or not and I'm going we use that.

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So it is called textfield should return the squarehead scope.

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And as long as you are programming in Swiftie can just type a little part of that code and will automatically

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auto complete it for you.

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So I'm going to say textfield Should that.

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And it says or should return.

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Is that the one you're looking for.

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And as you can see the return if it is a boolean.

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So I'm going to say return true.

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So yes it has to do something but what should it do.

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So let's go ahead and quickly talk about that a very very simple case of this would be this.

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I'm going to go to a storyboard and I'm going to select my text and when a change return returned then

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to look like a done by then.

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Even though this isn't really necessary I like to do it so it kind of becomes more clear what you're

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doing.

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So a return key is a donkey and I'm going to say the moment that textfield should return function is

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a trigger before you return true.

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Do this textfield resign the first responder.

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And I'm sure you can guess what this is going to do for us.

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Is it going to essentially say every time you press the return button on this textfield get rid of the

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keyboard and then yes that should happen.

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So I'm going to go in here.

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I'm going to.

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Show me the keyboard by pressing on the screen.

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And if you don't see the keyboard is because your soft keyboard is not on.

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You have to go in here on Press command OK.

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So if I have command Cain here the keyboard disappears.

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If I had command again it appears and testing purposes doesn't really matter but when you're using the

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simulator keep in mind keyboard shows up here.

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So I'm going to say let's say high on had done and gets rid of the keyboard now you might be asking

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yourself so what is this text field argument that is in here that essentially calls that text field

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that has triggered this function.

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You can simply imagine that this may not be the only text field that you have in your interface.

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You might have two of those and then depending on which one is doing something you might want to do

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a different thing in the next example.

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I'm actually going to do that.

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I'm going to go ahead in here I'm going to use a different delegate function called Text field.

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Should change should change which is this which essentially says Should I change the value that you

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are typing in a text field or not.

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Now let me quickly explain what is this useful for.

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Imagine a situation like this and we saw this sometime in the past that we wanted to have a text field

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that we can only enter numeric values.

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So two three to four would be valid values but effort would end.

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So we can actually use this function textfield should to change Kerak there to decide whether it should

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actually change or not.

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So practically by the end of this exercise we should be able to do this.

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If I were going here I'm press tree that should appear.

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But the 5:01 press pass that shouldn't appeal it should just be returned as a false value.

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So let's see how I'm going to do that.

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The first thing I'm going to do is I'm going to get myself a little bit more space and then I'm going

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to go ahead and say this is the logic that I want to do.

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The logic is this.

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Let's get all non numeric values.

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So these are things such as a s b c the com dot dot I all the star and whatever.

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Anything that is non numeric value that you can use get by a keyboard.

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Then I'm going to say let's get our string this string.

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We are trying to enter and divide that by these guys.

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What does that mean.

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Let's say a string is this.

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Those are the numbers.

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And then H-G some random characters and then those numbers.

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All right if I go ahead and divide that this string by the characters that are here then non-numeric

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characters we call that one card.

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If I divide it by non-numeric character I have this I will have the first part which is that I'm dividing

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by disguise etch j u s f d g.

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And if I had one more you know percentage in here.

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So that would be the first part and then I would have the next part which is four five six which is

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that and that I would have that last part which is a 78.

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So if I break my text against these dividers then non-numeric characters I will end up with this.

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The next thing I'm going to do is I'm going to say let's join all of these things together which becomes

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our previous pasted there.

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All of them together then I'm going to say compared the original text.

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This one against this new one.

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If they all the same it means I didn't have any non-numeric character.

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It means everything was numeric.

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But if they are not the same it means that something has gone wrong and I have an unusually quiet you

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and I should return true.

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So that's the logic of what I want to do.

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Let's go ahead and actually do the the first thing I'm going to do is this.

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I'm going to say let's call it numbers.

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Becomes are all of these guys which is very simple so we first get all the numbers all the things that

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we wouldn't like to have.

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Right.

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Then the next thing is I'm going to say let's let's call it.

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Remove the heart set.

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So this is the characters that I would like to remove and that's going to be on.

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And this character sets the targeteers in numbers.

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So that is my character set but this is the actual character set of the numbers not the ones I want

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to remove.

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So because I want to remove them I'm going to say well you know what.

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Get these guys and then do what we call inverted.

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So reverse it.

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Get these guys and then find everyone who is not to these guys because I could go ahead and manually

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try to type those but it would be a very very long set of characters.

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It would be a b c d e f g Hosh.

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All the way to Z and then the capital letters of all of these things and then every value that is non-numeric

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such as these guys so on and so you would become a very very long string and it would be very tedious

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to find them.

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So instead I said let's get the numbers on.

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Invert them.

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Once they have the inverted version I'm going to divide my a string Vider.

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So let's call it divide and this thing I want is this one the input string that the text field is providing

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for me.

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So that's going to be very simple.

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I'm going to say Let's call this one or a split or separate and separate it becomes a string of dot

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components and separated by remove characters that are separated by doors.

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So by now I've got all of these pieces separated and by now I have this data guy and that one on that

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one because I'm separating against a character set which is anyone but these.

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So it really gets rid of that part.

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And at that point.

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So then I'm going to go ahead and do what you suggest.

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I'm going to join them back to each other.

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So let's call this the join and the join is actually going to be let's call it join the string that

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becomes anything that we had here.

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Separate it separate that just joined and then it says how do you want to join in three.

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And I want to join them using a separator.

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What is the separator.

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Nothing.

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I want to join them right to one after another.

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I don't want to join them for instance by a space.

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If that was the case it would become something like this.

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But they want to join them exactly the way they are put them one after another.

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So I get that part done and then the next thing I'm going to do and when I say well I have that one.

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Now effect here is that if you have a string that was the original one is same as joined which is essentially

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this comparison.

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Then you have to return true and else you have to return false.

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Now let's see quickly what we did once again off the top.

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All right I'm going to get rid of all of this and when I say textfield should change tack then inset

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is a method that gets called from the textfield delegates.

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And it says every time you change something I'm going to call this function I'm going to fire this function

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but it's going to be up to the return of it whether I'm actually going to make that change or not.

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Now for me I'm going to go ahead and say these are the numbers.

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This is the characters that's built from those numbers inverted.

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So I get everybody who is not to these guys get my text string that is received in here separated by

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these characters.

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So if there is a number just keep the numbers separated by those values combine them back with each

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other.

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And once you combine them back and I think I need to be like that once you combine them back with each

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other compare them against each other.

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If it was the same as it used to be at the very beginning it means nothing changed.

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If it wasn't returned Fox.

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Now I was going to change this little bit to a much easier syntax.

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I'm going to say this is a true or false statement.

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If a string is joined and then if it is true we're going to return true if it is false return false.

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So what if we just return this guy that's it's going to say to return a string.

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Is it equal to joint.

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And if it is true it is going to return true if it is for us is going to return false.

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Now let's set this up in practice.

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I'm going to load up the app in my simulator and in here we should see if I'm going to boot up the keyboard

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when I try the text values.

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Nothing shows up then I go to the numeric ones everything works.

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Any one else.

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Nothing happens only numeric values and numbers can work.

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So we could actually combine this by saying my text field dot keyboard type is a keyboard type dot numeric

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keypad or a number power or something like that.

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And of course on the simulator you can not change the type of the keyboard but on actual device you

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could switch back to a different kind of keyboard but here we make sure our user absolutely enters numeric

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values.

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So that's about that using the delegation and finding the kind of you know functions that you have in

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a certain delegate and how you would use them.

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Like I said in towards the end of this section a few lessons from now I will show you much easier ways

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of finding the delegate methods.

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What is available in there.

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In all fairness a lot of the things that we don't know is just simply that when you decide to do something

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and you you come across an issue then you think to yourself that there might be a delegate method that

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does something like that.

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For instance there is another delegate method which I kind of forgot its name but they can show it to

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you here.

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This is the place to delegate.

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It means what happens when something gets pasted into my text field.

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Do you want to either know pop a little window saying like the one that you have on safari on iPhone

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that says the moment you paste something it says Do you want to search for this or do you want to automatically

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run the search.

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Well a lot of Obstat they allow you to enter text as an authorization when they send you a S-M mess

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with a number.

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Then you enter the card.

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There's one two three four.

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The moment you enter the 12:56 it automatically starts checking for authentication.

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So based on that you can do a lot of things and a lot of times you wouldn't exactly know what is in

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a delegate.

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You have to go through the manual and with the help raise resources read about them and find out you

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know what you could do with them or more importantly if you have a situation how you could fix it using

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any of these.

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So let's keep that up to here and then we'll move on to the next lesson which I think will do the same

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thing in Objective-C.