Swift协议一致性

Question

Here is an example of a set of value relationships that I am toying around with.

protocol Configurable {
    func configure(data: Any?) -> Void
}

class RelatedObject {
    var x: String = ""
    var y: String = ""
}

class Example {
    var a: String = ""
    var b: String = ""
    var c: String = ""
}

extension Example: Configurable {
    func configure(data: Any?) //I want the parameter to be of type RelatedObject?, not Any?
    {
        if let d = data as? RelatedObject { //I don't want to have to do this every time i implement Configurable on an object.
            //do stuff
            a = d.x
            b = d.y
            c = d.x + d.y
        }
    }
}

Is there a way for my classes that implement the Configurable protocol to be able to restrict the specific type of object they accept within the function signature?

I feel like Swift would/could/should have a way avoid a situation where I have to check class types for what gets passed into my object that I want configured.

Answer 1

You are looking for typealias in your protocol definition.

protocol Configurable {
    typealias InputData
    func configure(data: InputData) -> Void
}

In anything that implements your protocol you set the typealias to the type you would like.

class RelatedObject {
    var x: String = ""
    var y: String = ""
}

class Example {
    var a: String = ""
    var b: String = ""
    var c: String = ""
}

extension Example: Configurable {
    typealias InputData = RelatedObject 

    func configure(data: InputData)  {
        a = data.x
        b = data.y
        c = data.x + data.y
    }
}