Tuple with `let` or `var`

Question

Let's say I have something like this:

func myFunc() -> (Any, Any)? {...}

func anotherFunc() {
    if var (a, b) = myFunc() {
        // a is mutated and accessed; b is accessed, but not mutated
        a = b
    }
}

I need var for the tuple as a is mutated, but Xcode complains that "bwas never mutated, consider using let" - which is a somewhat reasonable argument, but I can't really define the tuple as (var, let).

I guess I could use index to access the two elements instead of declaring them, circumventing this issue. But is there a better way?

Answer 1

If you use pattern matching (i.e with if case), then you can use the tuple binding pattern, which allows you to annotate the mutability of the bindings separately:

if case (var a, let b)? = myFunc() {
    a = b
}

This also uses the optional pattern x? in order to unwrap the result of myFunc(), given that we're now using pattern matching instead of optional binding.