Swift 3 first parameter names

Question

In Swift 2, it appears that the first parameter name is not always required when calling a function. Now in Swift 3, the first parameter name is required when calling the function. For example:

func frobnicate(runcible: String) { 
    print("Frobnicate: \(runcible)") 
}

Swift 2.2 allowed the function to be called by simply typing:

Frobnicate("Station")

Swift 3 seems to be requiring that we use the first parameter names of methods such as:

Frobnicate(runcible:"Station")

Is this the case with Swift 3 for all functions and methods or just certain situations?

Answer 1

Yes, this is right. Swift is fixing a language inconsistency this way (this was always required for initializers).

If you don't want to use the external parameter name, just remove it explicitly:

func frobnicate(_ runcible: String) { 
    print("Frobnicate: \(runcible)") 
}

You can read the full rationale in Swift Evolution 0046

Answer 2

You can read The Swift Programming Language (Swift 3) in i-Book. Also you can check this out in WWDC 2016: What's New in Swift

In Swift 3, by default, functions use their parameter names as labels for their arguments. Write a custom argument label before the parameter name, or write _ to use no argument label.

fun greet(_ person: String, on day: String) -> String {
    return "Hello \(person), today is \(day)."
}
greet("John", on: "Wednesday")

or

// This also works with Swift 2
fun addThreeNumber(_ first: Int, _ second: Int, _ third: Int) {
    print(first+second+third)
}
addThreeNumber(1, 2, 3)