Iterating over an array and updating value. error: '@lvalue $T5' is not identical to 'Int'

Question

I have the following syntax in Swift:

func basicFunction(anArray:[Int], aValue:Int) -> Int {
    for (var i = 0; i<5; ++i)
    {
        if anArray[i] == 0
        {
            anArray[i] = aValue  //I get an error in XCode
        }
    }
    return 1
}

I get the following Xcode error: '@lvalue $T5' is not identical to 'Int'

What am I doing wrong?

Answer 1

Function arguments are immutable by default, and the Swift compiler gives terrible error messages.

Anyway, because anArray is immutable, you cannot modify it. That's why you get an error message. Declare it inout:

func basicFunction(inout anArray:[Int], aValue:Int) -> Int {
    for (var i = 0; i<5; ++i) {
        if anArray[i] == 0 {
            anArray[i] = aValue
        }
    }
    return 1
}

Call it with an & in front of the array argument:

basicFunction(&someArray, 99)