UPDATE: For Swift 3.0 update please see end of this answer.

Hey :

Functions have parameters, and these parameters can have names:

Local Parameter name

• A local parameter name is used for the implementation of the function, so basically you can use this name in the scope of the function.

External Parameter name

• An external parameter name is used to label arguments passed to a function call, in other words, when you call a function.

By default, the first parameter omits it's external parameter name, and the second and subsequent use their local parameter name, as their external name.

For example.

// This function has 2 parameters

func someFunc(name: String, lastName: String){
print("Hello \(name) \(lastName)")
}


// When calling this function, it will look like this.

someFunc("John", lastName: "Smith")

Notice how the first parameters name is not being used. That's because it's omitting it. The second parameter was used, since it uses it's local parameter as external.

If you want to make the first parameter appear when you call the function, you have to specify it in the functions declaration.

For example:

// I am giving the first parameter an external name as "firstName"

func someFunc(firstName name: String, lastName: String){
print("Hello \(name) \(lastName)") // here we are using the local parameter name
}

// When calling the function it will look like this

someFunc(firstName: "John", lastName: "Smith")

Hopefully this quick explanation helps you understand what he is doing, and parameter names.

Good luck, if you have any questions please let me know.

With the upcoming release of Swift 3.0, there are some changes.

• External Parameter name is now called Argument Label
• Local Parameter name is now called Parameter Name
• You now have to implicitly ignore the Argument Label with _ , if you do not want to use it when calling the function. By default, parameters use their parameter name as their argument label.