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Welcome back again we're going to conclude our brief introduction into object oriented programming by

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topic but a blurb.

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By talking about polymorphism.

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OK.

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And man sometimes just the words I want to come out and they don't come out.

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But they came out supinely morphism that's a hard word and that's hard enough for it to say as it is

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and it's a question that's often asked in interviews for jobs which is funny.

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There was like can you please define polymorphism and you're like oh what do I say.

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Because the definition so hard the implementation of it is so easy.

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But the definition is pretty hard.

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So we're going to say define polymorphism define Pawley morphism

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the condition of occurring in several forms.

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The occurrence of different forms among the members of a population or colony or in the lifecycle of

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an individual organism.

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So it Socan this is just generic definitions right.

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Talking about having different forms occurring in several several different forms.

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Interesting right occurring in several different forms.

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Here's another one.

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Some Please find it in two sentences.

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Polymorphism allows the expression of some sort of contract with potentially many types.

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Implementing that contract whether through class inheritance or not in different ways each according

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to their own purpose coding code using that contract should not have to care about which implementation

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is involved only that the contract that the contract will be obeyed.

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I like that one a lot and this is a programming definition.

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So you're going to create a contract and then different things can implement that contract.

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But they do it in their own way and you're probably super confused right now.

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And you should be because that's the textbook definition that's compute.

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That's what they teach you in college.

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All right let's see if we can confuse our students and not teach them anything practical but teach them

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things that don't make any sense.

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So let's teach you whether or what they're all about get started with the playground here and we're

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going to call this one.

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Paul Lee more fearsome.

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OK put it here in swithe.

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That's great.

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The principle is so simple once you watch me it is going to be like that.

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And that's how you should lead in your interview questions by talking about.

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Well let me just give you an example instead.

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So what we're going to do here is we're going to create a class called Shape.

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OK.

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And we're going to a property in it called Area OK bar area of type double.

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It may or may not have a value and this will put an optional at the end of it and create a function

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called calque relate area to.

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OK.

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Now here's our base class and every shape is going to have a calculate area function.

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Ok so here's the advantage of working with a base class.

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For instance let's say we didn't do this and what I wanted to get rectangles area so I would say class

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and then I would have to go and see a rectangle.

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OK.

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And then I'd say our area of type double.

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And then I would say phunk calculate area.

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OK.

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And then area would be.

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And then we need to pass and to lengthen it with here right.

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So laying type double and width of type double.

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And then we would say area equals length times with.

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OK.

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And then all of a sudden the boss was like oh no we need to also create a triangle so we're like OK.

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Like triangle or like var area double and then we're like phunk calculate area.

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And then we get a base of type of all.

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And what is a base and height divided by two.

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I think so.

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So we get the height which is a double and then so we say you know area equals based times height divided

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by two and one just puts in print this is peroration.

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OK so we've got two classes both doing similar things.

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But look at this.

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We had to recreate the area property we had to recreate this property here.

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And you know what happens if in this case one programmer gets lazy and they're like calque area and

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this one is just like you know let's get area.

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So now things are becoming inconsistent and the parameters start changing.

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You know base value.

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And this is not really good.

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We're rewriting code.

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We can break our logic.

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This is all trash trash trust trash.

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Get rid of it you're fired.

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Can't work here anymore.

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I'm just kidding.

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I'd still hire you.

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OK.

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So how do we fix this problem.

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How to make things more consistent where we can use polymorphism and what we're going to do now instead

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is we're going to create a new class called triangle of course.

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But this time we're going to inherit from Shape OK inherit from shape and all we have to do is obey

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the contract which is calculate area.

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So what we can do is we can say I want to implement calculate area function and we override it completely

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and then all we have to do.

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Actually this is wrong.

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This needs to have the values in it so let's put a value of type double and value be of type double.

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OK.

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Now we can calculate the area like so and then all we need to do is say area equals valet or times Balbi

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like so divided by two and this is this and this is this and this is a try.

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And in this case over here we want a rectangle class Rectangle.

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And that's going to inherit from shape and we do the same thing here calculate area.

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But in this case area equals value a times vel B.

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So that's interesting.

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We've got two different shapes here.

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Implementing the exact same function but the logic inside is different and that is polymorphism.

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OK.

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This is one form ok with or this is one object or form of an object but that is taking different forms

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like so.

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OK so we were obeying the contract like we saw in the really great stack overflow definition our obeying

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the contract and both these cases but they're both doing something different.

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And we're still using the same parent class.

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And that's what polymorphism and you use it all the time.

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So next when you go in your job interview if you can't read the definition you're like well let me just

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give you an example.

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So when he says give me the definition of polymorphous and said Let me give you an example.

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Imagine that you have a shape class and you have to calculate the area of shape but you don't know which

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shape is going to be passed in at runtime.

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So food critic calculate area function and then we also create two more classes like a triangle or rectangle

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that inherit from shape.

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And then at runtime they can each perform their own area calculation and assign it into the area value.

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And so it doesn't have to know beforehand what type of shape you're picking because you have the different

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implementation for it.

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Or you could say something like that and then be like oh that's a really good example.

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You know the same thing you know if you're building a videogame you know you might have a you might

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have a humanoid class and a humanoid class is just you know a base parent class and then the humanoid

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class might have Orcs because they're humanoid they got hands and feet they can speak to the Elves but

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you know elves are magical and mystical they can do their own things and orcs are brutish and you know

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ugly.

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So they've got to put an ugly modifier on there.

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And that's actually real that's a real example in games like World of Warcraft and other things.

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They're using polymorphism and inheritance all over the place.

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So that is polymorphism simple principle to understand once you do it and you're going to do it that's

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it.

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Mark Bryce had slopes dot com polymorphisms.