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Now that we've got a better idea of how fields work inside of a class, let's discuss how they work

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when we are dealing with inheritance as we are with our class car down here.

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I'm going to uncommon everything in the bottom half this file right here, and as soon as I do, you'll

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notice we get an air around the new car call right here.

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So here's the issue.

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Our class car extends vehicle.

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Any time we create an instance of something that is a vehicle, we have to provide it a color or a string

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to use as the color.

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So the reason we're seeing this air right here is that we have to pass in a string that will serve as

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the color.

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So we could fix up this air by putting a string in like red like so.

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And as soon as we do that, the air goes away.

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I want to show you something interesting right now, our class card does not have a constructor function.

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That means that whenever we try to create an instance of car, typescript is going to automatically

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call the constructor in the parent function right here.

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So even though you don't see any reference to it, whenever we create this car right here, the constructor

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in the parent is being called for us automatically.

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And that's why we have to pass in that string.

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Things are going to be just a little bit different if we define the constructor inside of class car

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as well.

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So let's try that right now, I'm going to define the constructor function inside of car, and I'm going

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to say that this thing is going to have its own property like, let's say, public wheels.

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And this will be maybe like the number of wheels that a car has.

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So I'm going to annotate with the type of number like so.

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Now, as soon as I define this constructor, you'll notice Nasti Air inside of here, and if I hover

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over it, it says that the derived class must contain a super cool.

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The word super right here is a reference to these super class or the parent class of car, which is

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vehicle.

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So whenever we called a constructor of a child class, we are required to call the constructor method

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of the parent as well to do so, all we have to do is call super like so.

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As soon as we do so, we're still going to see an air here, so super right here is a reference to the

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constructor method in the parent.

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And once again, the constructor and the parent wants us to pass in a string so we can make this go

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away once again by putting in some hard coded string like so.

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But chances are we don't want to do that.

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Chances are we want to have the color still come in as an argument to our car when we create it.

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So maybe we should take in a second argument to the constructor function.

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That will call color, and it's supposed to be a string like so.

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Notice how I did not put the public key word on here I didn't put public on because we do not want to

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reassign or create a new field in car of color.

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The field color belongs to vehicle.

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So that's why I did not put on the modifier of public.

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So now when we call the parent class constructor through these supercool right here, we're not going

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to pass into hardcoded red.

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Instead, we can pass in the color.

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If we now go back down to the bottom of the file once more, you'll see we've got an area down here

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again.

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So now we are saying that our constructor for car has to be given a number of wheels as the first argument

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and a second argument of a string so we can fix up this error by putting in four wheels as the first

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argument.

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Now, the second argument is going to be a string, which is going to pass on through the constructor

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right here into the parent constructor of vehicle.

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And that's pretty much it.

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Now, I know we're going through this stuff really quickly.

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The reason we're going through it so quickly is that basically all the projects we're going to work

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on in this course are 100 percent focused on using classes to represent logic inside of application.

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So really, I'm just showing you all this class stuff right now to get you used to some of the very

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basic syntax.

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And we're going to really repeat all these different rules that we're going over in great detail throughout

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all these applications we go through.

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So hopefully you're just absorbing a little bit of the syntax here.

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That's really the only expectation I have.

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Now, having said all that, this is really all we wanted to learn about classes, so we've taken a

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look at Method's constructor's basic inheritance, super calls modifiers.

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That's pretty much it, the whole ball game.

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So let's have a quick pause right here.

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We're going to do a wrap up on classes in the next video, and we'll start working on some really interesting

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applications.

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So I'll see you in just a minute.