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Indices I'm going to show you how to make classes in Objective C in an ideal situation I would leave

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this up to you as an assignment or an exercise.

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But I think it helps if I give you some instructions at the beginning about classes in Objective-C.

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In theory they do exactly the same thing as the ones in swift.

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In practice they are a little bit different in how we called them.

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So let's go ahead to X go at the next one I'm going to start a new project command line.

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At this time is going to be an objective see one and I'm going to say this is called classes in object.

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See so the one big difference between when we do things in Objective science free is if you remember

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in objective C-v always had two files we had the dot h n m.

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And that's kind of for a reason that's there because they are to declare classes in two separate places.

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So to declare a class in Objective-C I'm going to say at interface and then my class name I'm going

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to call this one class to be a car for instance.

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And then unlike Strief classes in Objective-C absolutely need to have a super class or what we call

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a base class.

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Now a base class is essentially something that we inherit from.

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For instance you might be writing something that is a new feature to an array and then this would be

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common in this array.

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I'm trying to make a subclass of an array.

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If you don't know what subclass you have to use it's not exactly scientific.

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But as a rule of thumb you can say you don't know what's the superclass.

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I can stick to a subject but most likely you wouldn't know what to use.

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For instance when we make an appt.

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You don't need to do this part.

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I'm just going to show it to you.

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Then we make a template up.

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If you remember our interfaces in our view controller are subclasses of you eye view controller simply

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because my view contouring needs to inherit things from your view controller.

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We'll talk about this more when we talk about inheritance there's going to be a lesson about that.

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But for now if you're making an interface and you don't know the superclass of it you can live with

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a subject.

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Once you have a class interface or you have your class figuration.

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I'm going to have to go ahead and add an implementation.

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And that's essentially saying what are the different a specification of my card.

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This is exactly like the one that I'm going to reopen this.

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Again is exactly like the one that we have in view controller data and that's the implementation of

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our view controller.

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If you remember I told you we can get rid of this private interface and then we have the implementation

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view controller and we have the interface View Controller.

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So in here we have the same thing.

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Once we have an interface of car we have the implementation of the car.

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He's asking me to write the methods for it.

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So let's go ahead and add a few properties or attributes to our core and then some methods.

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The first property that I want to add and we are like this property and this thing is going to be called

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a name that is the name of the car object we're about to make.

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If this was a real car in let's say a game that you're writing it would have model and color is speed

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a number of years so on and so forth for now and then have only one more and that is property that's

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going to be a boolean property is called ease on which essentially defines whether the car is currently

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on or not.

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I'm also going to add two functions or two methods to our cars.

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I'm going to say one of them is art.

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The engine on.

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So that's one method that's going to turn the engine on and they want to have an in it I want it initialises

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I want any show they want to override my initializers.

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So this one is a little bit different than what we had in in swift so in here.

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As always when we are writing something we have to actually tell it what kind of return type it has

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and the return type of it will be something that we call instance type means of whatever is the type

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of this car return that same it means when you are writing this method if it is going to be or initialiser

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return it of the same type.

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The next thing which is very important it has to begin with in it its name has to have in it.

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And then you can add whatever you like and will say in it with the state on what's the estate.

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The estate is a Boolean OR they call it our current or is beginning a start a state.

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So that's essentially initializing a car with a beginning or a starting state.

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Imagine you have your car on at the very beginning or you want the engine to be off at the very very

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beginning.

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Now so far and I think that this may drop that.

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So far we have managed to write an interface for a car a class declaration for car two attributes and

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two functions one of the two functions is in its function.

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The other one is just a function that does something.

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So now Isaac squaddies right reminding us is saying that the definition for these two methods are not

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there.

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His things are what you want to do with these two methods.

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So I'm going to say well one of them let me copy both of them actually but easier to copy than to retype

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everything.

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I'm going to say in both of them I want to do some things.

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So one of them turn engine on is actually very easy.

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I want to say whenever this function gets called ease on it becomes true.

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So if the engine is off it becomes on even if it is on stay still comes on.

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Now the other method the initialization needs a little bit of explanation.

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First of all it has to return something to the team.

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It has to return is essentially going to be of the same type or it is going to be self so I'm going

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to say first of all and that's the end return.

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But then we have something very simple which is is on has to become the very start that we have.

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If you want the engine to start on that would become on if you wanted to be off that would become off

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I would become false essentially.

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The last thing which is actually here the first thing you have to do we have to say self is super super

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in it and that's simply because our class actually has a superclass.

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So we have to say in a nutshell when you are initializing first initialize this object now that in a

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subject and here is I'm kind of bleeding into the inheritance here we are saying car is an object that

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has a name and he's on.

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So I'm saying first of all make out on a subject to initialize that once you did that for this instance.

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Change is on to something new and then return it to us.

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And that's about that.

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That's everything we needed to do.

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So really quickly keep an eye on this so you know what's going on.

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Once you are happy with the small one to initialising this for the first time.

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So now I'm going to go to my actual program I'm going to say color on this car is called a jeep and

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this is going to be car lock and in it it could either do it like that or you could say car.

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Let's call this one a whole lot.

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And that's going to be car lock and you need to get a state.

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And I'm going to say Drew.

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So both of them are valid.

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Most of them are the ways that we could use them.

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So that's how you declare a class in Objective-C.

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That's how you introduce attributes to it.

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That's how you do functions.

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And this is in particular how you do and emits methods for it.

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And then of course in the end it meant that you have to return the self and the self has to be whatever

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it is to particular US which in Objective C is mandatory as opposed to Swift.

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And then when you're using it this is like everything else that we have seen and as an array my array

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is an array of locks.

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And it.

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Right.

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That's exactly the same thing as we have in here.

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Except here is called Car overlays and Asare or any other state.

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And remember we had in it with objects we could actually add a stuffed with on the fly at the initialization

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level.

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So that's about that.

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That's how we managed to add classes to our Objective-C program.

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And that began to move one.