[SOLVED] Array.map(String.init): what happens here?

Array.map(String.init): what happens here?

let iNumbers = [1, 2, 4, 8, 16]
let sNumbers = iNumbers.map(String.init)
print(sNumbers)

// I would expect (and understand) something like this:
let sNumbers2 = iNumbers.map { num in
    String(num)
}
print(sNumbers2)

What does String.init do? It's not even a proper method call.

Can someone give some explanation?

Solution

It's the same, because, map can take a function / closure as its input parameter or expose to the outside (as your sNumbers2).

@inlinable public func map<T, E>(_ transform: (Element) throws(E) -> T) throws(E) -> [T] where E : Error

So:

iNumbers.map(String.init)

//is a shorter way and equivalent to

iNumbers.map { num in
    String(num)
}

//and also the same if your have any function that return a String
func convert(_ input: Int) -> String {
    String(input)
}

iNumber.map(convert) //<- still valid ✅