All language subtitles for 005 Functions in Dart_en

In the last section, we broke down this line of code right here, remember, the VA name is referred

to as variable declaration because it creates a new variable then the equals.

My name is referred to as variable initialization because it assigns a value to that new variable that

was just created.

At the end of this line, we had a call to the my name function, which was defined down here at the

bottom of the file.

So in this section, we're going to start to take a look at this function declaration down here.

Now, I don't have a terribly large amount to say about functions, mostly because they work almost

identically to how they work and just about every other style language out there, every function we

create can have a name assigned to it.

So in this case, the name of our function is simply my name.

After the name of the function, we then place a set of parentheses which denotes the argument list,

so any time we call a function, we can pass in some number of arguments to it.

We then have a set of curly braces which form the function body.

So inside those curly braces is where we add all the code that's going to be executed any time we call

this function.

And where things start to get a little bit interesting is the word string over here to the left hand

side.

So any time our function returns a value, we can annotate that function with the type of value that

is going to be returned in this case, we are returning a string from the function.

So we wrote out the left hand side of the function name string, because that is the type of value that

we're going to return any time this function gets called.

We're going to have a discussion about type's in just a second, but before we do, I want to mention

one other thing about functions in darte.

Back over here, you'll notice that we had a function called Main, and then we had also defined a second

function called my name in general.

You and I can name functions, anything we wish.

But there's exactly one exception to that rule, and that is the main function in darte.

The main function is a very special function that has to be defined inside of every darte program that

we ever put together.

The main function right here is automatically invoked by darte any time our program is executed.

And so you can kind of think of the flow of operations as being something like this.

So we're up here at the top.

Our program starts up darte, is going to look over all the code inside of our application and try to

find a function called main.

If it finds it, it's then going to run it.

And from that main function, you and I can add some code to do some actual up of our application and

accomplish whatever app is really trying to do.

Now, one thing I want to mention here is that every darte program we put together has to have a main

function.

So, for example, if I take this entire main function back here and delete it and then click run again.

You'll notice that I get an error message over here on the right hand side that says uncaught and essentially

it's an error message that's complaining that there's no main function defined inside of my project.

If I go back to having the main function and run it again, I'll then see the expected output of my

name is Stephen.

So in closing, functions for the most part behave very similar to how they do in just about every other

language out there.

The one requirement of every program is that we have to have one function called main.

The only thing that's kind of unexpected about these functions is that they have to annotate their return

type with a type being listed just to the left of the function name.

Now, let's take a pause right here.

We're going to come back to the next section and we're going to start talking a lot more about how types

work in DART.

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