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iOS

Posted by chrisverra
chrisverra
3,760 Points

i have to give the second parameter name to function?

It only works like this for me:

func calculateArea(height: Int, width: Int) -> Int{
    let area = height * width
    return area
}
calculateArea(5, width: 7)

i have to say width, i cant say width + height, that gives me error.

howcome it has to be this way?

3 Answers

Jhoan Arango
Jhoan Arango
14,575 Points
Jhoan Arango
Jhoan Arango
14,575 Points

Hello Chris:

I believe your question is about naming your parameters. When creating a function, you can give its parameters names, so that when calling the function is more readable.

They consist of Local, and External names:

  • Local Parameter Names : Are used for the implementation of the function, so you can only use these names locally, meaning with in the function's body.

  • External Parameter Names : Are used to label the arguments passed into a function.

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

Here is an example of a function

func sayHello(to person: String, and anotherPerson: String) {
    print("Hello \(person) and \(anotherPerson)")
}

// Calling the function

sayHello(to: "Chris", and: "John")

// Prints "Hello Chris and John.

Hope this helps you understand a bit more.

Good luck

chrisverra
chrisverra
3,760 Points
chrisverra
chrisverra
3,760 Points

Hi John,

I did understand this part, but thanks for clearing it out even more.

The thing i did not understand is when i call the function like this:

// note that i removed the parameter names
func sayHello( person: String,  anotherPerson: String) {
    print("Hello \(person) and \(anotherPerson)")
}

sayHello("Chris", anotherPerson: "John") // howcome I HAVE to give the name of the second paremeter
// and howcome I am NOT even allowed to also give the name of the first parameter
Jhoan Arango
Jhoan Arango
14,575 Points
Jhoan Arango
Jhoan Arango
14,575 Points

Chris:

Notice how in my explanation it says that the first parameter omits its external parameter name. 

func sayHello(person: String, anotherPerson: String) {}

// calling this function 

sayHello("Chris", anotherPerson: "Jhon")

Since we didn't give the first parameter an external name, then when calling the function, that name will not appear. The second parameter name uses its local name AS the external parameter name as well, hence the reason why it appears when calling the function. 

func sayHello(person: String, _ anotherPerson: String) {}

// Calling function

sayHello("Chris", "Jhon")

If we use _ before the name, it will then ignore the external parameter name when calling the function.

For a much better explanation, please click here and scroll down to look for " Function Parameter Name.

Good luck