Swift: array of structs implementing protocol

Question

I can't understand why I can't pass an array of structs (which implement a protocol) to a function expecting an array of things that conform to that protocol.

I get a compile error at: r.setDataToRender(toRender) --> Cannot convert value of type [Process] to expected argument type [MyType].

What I can do is to create an array [MyType] and append each element of toRender and pass that new array instead, but that seems inefficient.

//: Playground - noun: a place where people can play
typealias MyType = protocol<Nameable, Countable>

protocol Nameable {
    func getName() -> String
}

protocol Countable {
    func getCount() -> Int
}

struct Process : MyType {
    let processName: String?
    let count: Int?

    init(name:String, number: Int) {processName = name; count = number}
    func getCount() -> Int {return count!}
    func getName() -> String {return processName!}
}

class Renderer {
    var data  = [MyType]()

    func setDataToRender(d: [MyType]) {
        data = d
    }

    func setOneProcessToRender(d: Process) {
        var temp = [MyType]()
        temp.append(d)
        data = temp
    }
}

var toRender = [Process]()
toRender.append(Process(name: "pro1",number: 3))

let r = Renderer()
r.setOneProcessToRender(Process(name: "pro2",number: 5)) // OK
r.setDataToRender(toRender) // KO

var str = "Hello, Stackoverflow!"

Answer 1

It works if you change it to this:

var toRender = [MyType]()
toRender.append(Process(name: "pro1",number: 3))

Your function setDataToRender is expecting an array of types MyType . When you instantiated your array you typed it to Process . Although Process implements MyType it is not identical to MyType . So you have to create toRender as an array of types MyType to be able to send it to setDataToRender .