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All right.
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So in this module, we're going to look at how we can use Realm to persist our data, instead of using Core
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Data.
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If you have never come across Realm, then it's a good idea to familiarize yourself with it by going to
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realm.io. And they've got a whole bunch of educational resources, as well as tutorials, example apps,
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and also a really, really good documentation.
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So what we're going to be using is the Realm database which is an alternative to SQLite
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and Core Data, and it's also open source which is great because if you wanted to dig in and look at how they implemented 
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their core, then you can do that.
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So we're going to head over to Products, Realm Database, and we're going to pick our language as Swift,
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and this takes us to the Swift documentation.
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So if you wanted to look at the source code, then you can go to Realm Swift and you can dig through all
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of these files. But I'm going to show you how to get started.
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So in order to install Realm, there's three ways. You can either download the Framework or use CocoaPods,
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or use Carthage.
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And I, as always, favor CocoaPods.
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Look at how short it is compared to everything else.
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And so this is what we're gonna be using.
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So let's head over to our project.
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We're going to close it.
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Going to open up Terminal and we're going to locate our Todoey folder,
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so the one that, of course, contained the Todoey.xcode project, and then we're going to cd to it.
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And if you're interested in speeding up your workflow, you can actually change commands in the Terminal
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together by just using a semicolon.
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So we're going to change directory to the Todoey folder, and then we're going to perform "pot init" at
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that location, and then we're going to say open Podfile in the application code Xcode, and we're gonna
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hit enter. And now it should go through and perform all of those things bringing us to our Pod file.
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o now I'm going to uncomment this line, so that we're targeting platform iOS 9.0 and above
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and we are going to use frameworks. And the Pods that we're going to incorporate is one called
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pod 'RealmSwift' and this has dependencies
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so we'll also pull in the Realm framework as well.
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So we're going to hit save, close that down, and go back in here, and say "pod install." All right.
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So after a little bit of waiting, you can see it's now done, and it's installed the latest versions of
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Realm and Realm Swift by just simply saying Pod Realm Swift. Now, currently, the latest version of Realm Swift
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is 3.0.2 and that is the version that we're pulling in through CocoaPods as well.
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So just check and confirm, and then we can close down Terminal and we're going to go back into Finder
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and open up our text code workspace file.
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All right.
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So here's our brand new Xcode project with those pods incorporated
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and let's just expand all of our folders so that we can see it clearly.
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And as you can see, as soon as we install Realm, we've got this warning in our status bar here.
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And it says that your pods including the Realm and Realm Swift need to be updated to recommend settings.
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This is not a problem though because if we just click on this warning, then it will update all of these
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things automatically for us. I'm going to hit perform changes and it's all good to go.
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And that's it.
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All right cool.
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Okay, so the first thing that we're going to do is we're going to go over to our AppDelegate and we're
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going to try and create a brand-new data entry in our Realm database.
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So inside here the first thing that we need to do is we're going to have to import RealmSwift, and as
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always, usually, with CocoaPods. It might not recognize your modules when you first open up your Xcode
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workspace.
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So if it does this, and you can see, for sure, that there it is, then you can simply go and hit command
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B to build and it should get rid of that error for you once build complete.
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Now, we're going to write our code inside the application didFinishLaunchingWithOptions delegate
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method.
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And here we're going to first create a brand-new Realm. So you can imagine Realms as almost like different
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persistent containers.
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And we're going to call it realm,
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so let realm equals a new object from the Realm class.
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Now that would be great if that just worked as is.
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But unfortunately, the initialization of a new realm is actually marked with throw,
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so it can, in fact, throw an error.
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So we have to market with a try which means that we probably need a do catch block.
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So, now that's a little bit safer.
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We're going to use it to save a new piece of data.
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So Realm allows us to use object-oriented programming and persist objects.
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So let's go ahead and create a new Swift File and let's call it just Data and it's going to be grouped
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inside the Data Model folder. And inside Data, we're going to be using Realm,
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so I'm going to import RealmSwift, and then I'm going to create a new class.
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The class is, of course, going to be called Data and it's going to subclass something called Object. 
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An Object is a class that's used to define Realm model objects.
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So it's a superclass that we're going to use to enable us to persist our Data class. And the code inside
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is going to be where we're going to declare our properties for the Data class.
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So, say, if the data that we needed was a variable code name and it was of type String and it starts off
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with a value of an empty string, and another one called age and it's of type Int and it starts off being
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0.
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So under any normal conditions if we weren't subclassing object and we were just creating a new class
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to represent our data, then this would be fine.
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However, because we're using Realm, we actually need to mark our variables with the keyword "dynamic." And
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there's a long and short answer as to what dynamic means.
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So the complex answer is that dynamic is what's called a declaration modifier.
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It basically tells the runtime to use dynamic dispatch over the standard which is a static dispatch.
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And this basically allows this property name to be monitored for change at runtime, i.e., while your app
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is running.
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So that means if the user changes the value of name,
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for example, while the app is running, then that allows Realm to dynamically update those changes in the
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database. But dynamic dispatch is something that actually comes from the Objective-C APIs.
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So that means that we have to mark dynamic with at Objective-C to be explicit that we are using the
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Objective-C runtime.
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Now, the simple answer as to why we just added these two keywords in there is that we need to add these
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two modifiers, basically, so that Realm can monitor for changes in the value of this property,
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and this is what we'll allow us to do it while the app is running.
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So let's go ahead and add that to our second variable as well,
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so they are now both compliant with how Realm properties should be declared.
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So whenever you're declaring a new property that's any of the basic data types, you will need these two
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keywords in front of it.
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Okay.
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So, now we can go into our AppDelegate and we can create a new piece of data that is going to be an
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object of the Data class and we can set its properties by saying data.name
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= "Angela" data.age equals-- I'm not going to say my real age here,
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right?
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Let's say, I'm 12.
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All right.
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So let's go ahead and add our new item, i.e., create in CRUD, and we're going to commit the current state
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of our Realm.
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So just as we did with Core Data, we basically created a new piece of data,
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then we used the context to commit the current state to our persistent container, or in this case, it's
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our Realm database.
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So in order to do that, we can move this down here.
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And after we've created this brand-new Realm, we can then say realm.write
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which means commit the current state persistent storage or to our Realm database, and then we can say
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realm.add a new object, and a new object is going to be our data.
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So as with initializing a new Realm, realm.write can also throw.
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So we have to also market with the "try" keyword which is why they're both kept inside this do block underneath
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where we created our data.
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So, now all we have to do is run our app so that our application didFinishLaunching gets called and
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all of this gets implemented so that we'll be able to save our data to our Realm database.
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All right.
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So that worked without any issue.
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But how do we view our data because we're not using it to populate any of our table views? This is still
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using Core Data,
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remember? And all of our code is inside the aapp Delegate.
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But if we have a look in our debug log, we didn't get any errors coming back, right?
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So that means our process probably completed successfully.
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So our data did get saved into our Realm.
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So in order to locate where our data is stored or where our Realm database is, we can use a print statement.
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We can say print (Realm.Configuration.
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defaultConfiguration.fileURL. And this is the location of the Realm file.
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And now, if we print that out, we'll be able to locate where our Realm database exists. Now, because we're
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not unwrapping it,
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it's gonna get printed as an optional.
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And there it is.
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So that's our file location.
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But before we can view this file, you can see that the file is actually something called
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default.realm.
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So it's a Realm file.
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So in order to see the data that exists inside, we need to download a piece of software from the App
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Store.
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And it's a free Mac app called the Realm Browser.
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So if you search for Realm Browser inside your App Store,
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then you'll come across this Mac app made by the round team and it's free to download,
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and it's quite a small piece of software.
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Only, what, 5.9 megabytes. And you can simply download it onto your local machine.
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But once you have done so, then you can open up your Realm Browser and you can click on the open realm
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file.
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So, now it's going to take you into your file browser and we're going to have to navigate to that location
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that we printed out earlier on.
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Now, previously, I've always shown you the sort of bog-standard way of navigating to a location in your
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file directory which is chasing the directories,
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right?
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But it's a little bit painful.
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So let me show you how you would do it as a shortcut.
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So if you hit command shift G, then you can actually go straight to the folder or the document. And all
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you have to do is take this string that says a file something, and all the way down to Realm without copying
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any of the Realm brackets, hit command C to copy, and then we're going to hit command V to paste.
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Now, if you navigate to the front of this string, if you delete the file, colon, dash, dash, so you only end
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up with a forward slash, user, slash,
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angelayu, this is your file path that will help the Finder to navigate to this location. And then you can go
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ahead and simply hit Go, and it takes you straight to that location.
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Now, you might think I'm a little bit sadistic for making you guys go through this process many times
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previously, but it's always good to know how it's done manually before you learn about shortcuts because
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a lot of people learn the shortcuts first, and then when you get stuck or when something doesn't work,
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then it's always very confusing.
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So there's always the long path to fall back on, but to save your sanity and your precious life, then
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it's a good idea to use the file path to navigate. And you can do this in any Finder, not just in the Realm
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browser,
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by the way. So if you're inside any sort of Finder window and you're trying to locate something, you can
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simply hit command shift G and you can go straight to that location.
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Now that we're here inside the Realm browser, we can simply select our default.realm database and
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we can hit Open. And Realm will need access to this path,
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so we're going to have to click Allow and you might even have to enter a password every now and then.
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So we run our app twice, first time to check that it worked,
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and the second time, to get this file path.
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And that means that our application didFinishLaunchingWithOptions got called twice which means that
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we saved two pieces of data both with name Angela and age 12.
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And you can see that the Realm browser is this really, really simple interface where you can see your
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models,
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so our Data Model, and you can see your properties: name which is a string, age which is an integer.
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And we've got our pieces of data and it even shows you the minimum, average, maximum, the sum, and some
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simple bits of analysis on your data.
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So that was pretty pain free, right?
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And compared to how much work we needed to do in order to set up our Data Model using Core Data,
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I hope you can see that this is a very, very useful tool. And we're going to dive deeper into Realm in
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the next lesson, so that we can start working on how to do CRUD using Realm, instead of Core Data.
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And you're going to see all of the ease and the shortness of the code and all of the beauty of this new
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way of doing things.
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So for all of that and more, see you on the next lesson.