Swift protocol for string interpolation

Question

What protocol do I have to implement to control the way an object is represented within a string interpolation in Swift?

I wan\'t to specify what get\'s printed in somet

Answer 1

I would like to put an alternative solution here:

The protocol for string interpolation in Swift is StringInterpolationConvertible. That is, any class which implements the protocol, can be constructed from a string interpolation.

Back to the question, to control what is printed out for a String string interpolation of instances of class A, you would need to create a String extension and overload the init(stringInterpolationSegment expr: A) function.

extension String {
    init(stringInterpolationSegment expr: A) {
        //do custom work here
        //for example: self.init(expr.description)
    }
}

In case you are looking for a way to remove the annoying "Optional(...)" when interpolating Optional variables, which I think is the main reason why people would want to control how an object gets printed out, just have a look at the pod NoOptionalInterpolation here.

Additional information (edited): Confirm that overriding description will only work for your own struct/class, but not for existing struct/class such as Int and Optional.