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swiftinout

"&" in "swap(&someInt, &anotherInt)". What does it represent? What is its function?

I'm new to Swift and I'm trying to learn the concept of 'inout' keyword. I saw this code in "the swift programming language 2.1". My question is, why is there a "&" in "swap(&someInt, &anotherInt)". What does it represent? What is its function?

func swapTwoInts(inout a: Int, inout _ b: Int){
    let temporaryA = a
    a = b
    b = temporaryA
}

var someInt = 3
var anotherInt = 107
swap(&someInt, &anotherInt)

print("someInt is now \(someInt) and anotherInt is now \(anotherInt)")
Solution

  • Just like passing by reference in C++, the ampersands in the calling bit of the code just tell the compiler that you give permission to function swapTwoInts to change both someInt and anotherInt. If you had not put the ampersands there, the code would not compile.