All language subtitles for 013 Review on Constructors_en

In the last section, we spoke about constructor functions defined on classes.

We also went through a little bit of a shortcut on assigning a property straight through the constructor

without having to add any additional function code to the constructor itself.

So in this section, we're going to do a quick review on what just happened, just to make sure that

it's really crystal clear, because this abbreviated syntax right here of initializing a property name

directly from the constructor is something that you're going to see all throughout this course in a

tremendous amount of documentation on D'Arte as well.

So let's get to it.

And I put together a quick diagram to help you understand what is going on.

And the first thing I want to remind you about is that you and I added a function to the class.

The functions name was person with a capital P because that function name was absolutely, positively

identical to the class name.

It became the constructor function for this class automatically.

Remember, a constructor function gets called automatically any time that's been defined on the class,

and it is our place to do some initialization or setup of the class instance.

Inside this constructor, we specified an argument list with exactly one argument on it, inside that

argument list, we wrote out this first name.

This means that in order for us to create a new instance of a person, we have to call a new person

and provide exactly one argument to it.

So specifically because we wrote out an argument right here that means any time we create a new instance

of a person, we have to provide one argument as well.

Now, the interesting thing about that argument that we listed there was that on the front of the argument

name we put on this dot and then we wrote out a property name or the name of a property or field that

belongs to this class because we followed that strict rules because we have this dot and then exactly

the field name right here darte decided to automatically take this argument of string, Stephen, right

here or whatever your name is in your case, and automatically assign it to the first name property

for us.

So again, specifically because we used this dot and then the exact name of the property, this got

assigned to the correct property name for us to give you a very, very quick demonstration of exactly

how that worked.

I'll flip back over to Pat over here.

Now I want to find that constructor function and I'm going to try changing first name right here to

something else, like maybe something like my first name.

Now, when I do so, you'll notice that I've got an error message down here, it says My first name

isn't a field on the inclosing class.

However, if I remove the this dot from this thing.

Then you'll notice that the error message goes away, so it's specifically the combination there of

putting this dot and the exact property name that allows us to take this shortcut in adding this property

to the class person.

So I'm now going to revert that back to this dot first name and now my code is going to work as it did

before, exactly as we expect.

OK, so again, in the section we spoke about constructor's and we spoke about this little shortcut

right here for assigning fields to a instance of a class, whenever we call the constructor function

and we call that constructor function by using the new keyword right here and then referencing the class

name.

It's now that we've got a good overview on this, let's continue in the next section where we're going

to start working on our next project that's going to heavily involve classes.

So quick break and I'll see you in just a minute.