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swiftoperator-overloading

how to overload an assignment operator in swift

I would like to override the '=' operator for a CGFloat like the follow try :

func = (inout left: CGFloat, right: Float) {
    left=CGFloat(right)
}

So I could do the following:

var A:CGFloat=1
var B:Float=2
A=B

Can this be done ? I get the error Explicitly discard the result of the closure by assigning to '_'

Solution

  • That's not possible - as outlined in the documentation:

    It is not possible to overload the default assignment operator (=). Only the compound assignment operators can be overloaded. Similarly, the ternary conditional operator (a ? b : c) cannot be overloaded.

    If that doesn't convince you, just change the operator to +=:

    func +=(left: inout CGFloat, right: Float) {
    left += CGFloat(right)
}

    and you'll notice that you will no longer get a compilation error.

    The reason for the misleading error message is probably because the compiler is interpreting your attempt to overload as an assignment