not `fun foo(): Int {}`

# announcements

[Ifvwm]

not fun foo(): Int {}

[Derek Peirce]

fun Int.foo() { ... } is an extension function, called as 5.foo(). fun foo(): Int { ... } is a method that returns a value of type Int. These are not independent, you can also have an extension function fun Int.foo(): Int { ... } that returns an Int, which could be, for example, fun Int.foo(): Int { return this + 5 } .

[Ifvwm]

@Derek Peirce Int can be a base class, can it be a super class?

[Derek Peirce]

The extension method would work for Int and all subclasses of Int, although Int is not an open class and therefore cannot be subclassed.

[Ifvwm]

@Derek Peirce fun Int.foo(){ val c1=this@foo} what this c1 is?

[Ifvwm]

for example, 5.foo(), what c1 is in it?

[Derek Peirce]

Try running it in https://try.kotlinlang.org/ and see what happens.

[Shawn]

you should probably go through the Kotlin Koans, it covers a lot of the stuff you might not be familiar with from other programming languages

[Shawn]

there’s also a Kotlin guide for Python programmers if that’s relevant to you

[Shawn]

also the this@foo question is more or less answered by one of the docs links I shared earlier — you should try experimenting with examples in the docs in the Kotlin playground or in a scratch file, or even just in a main() function in your existing project