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In this video, we're going to continue discussing classes in typescript by taking a look at the inheritance

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system.

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So right underneath my class vehicle, I'm going to get started by creating a second class definition.

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I'm going to call this thing car like so.

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I want you to think about the relationship between a car and a vehicle in the real world.

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I think that we would say that a car is a type of vehicle and chances are that a whatever a car can

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do, a vehicle should be able to do as well.

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So, for example, a car should be able to drive and it should probably be able to honk as well.

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So we would probably want our class car to have essentially all the same methods or functions of class

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vehicle to make that happen.

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We could either copy paste all these methods down here like so, or alternatively, we could have our

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class car extend the vehicle class to do so.

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I'm going to find class car right here.

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And then right after I say extends vehicle like so I writing in this little additional syntax right

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here, we're essentially telling TypeScript that we wanted to take all the different methods inside

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of this class and essentially copy paste them over to class car.

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Now, there's not actually a real copy paste going on here.

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The actual system is a little bit more complicated and we're going to go deeper into that system over

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time.

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But right now, we can just imagine that by adding on extends vehicle, we're essentially taking all

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these methods and copy paste them down like so.

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Where we create a new vehicle down here, rather than creating a vehicle, we can delete all that and

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instead let's try creating an instance of a car so I can say consed car is new, car like so.

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And then on this instance of the class, we can now call all the different methods that we had associated

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with vehicle so we can say car drive and car don't honk like so.

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Now, if I say this file, flip back over to my terminal and run the file again, we're going to see

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the same output once again.

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When we have a class that extends another, we can optionally choose to override different methods.

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So, for example, let's say that we want our car class right here to have a different implementation

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of drive than the parent class.

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To do so, we can simply redefine drive inside of car.

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I'm going to again annotate this with the return type of void and maybe inside there for our car, rather

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than doing a console log of chug, chug, chug.

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I instead wanted to do a console log of, like, vroom like so.

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So if we now say this again and flip back over to our terminal, we can rerun the file once more and

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no longer are we going to do the Chugalug and we'll see Vroom instead.

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So we've successfully overridden a method on the child class.

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We refer to CAR as a child class because it is extending the vehicle.

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We would refer to a vehicle in this case as the superclass or the parent class.

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All right, now we've taken a look at basic inheritance, let's take another quick pause right here.

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We're going to address a couple more side topics around classes.