How to create an array of classes and instance objects with it in Swift?

Question

I tried to ask this question previously but didn't clearly express my question, so I'll try again here. I also noticed a very similar sounding question, but it is asking for something entirely different.

I have the following code:

class Base {
    func launch(code1: Int, code2: Int) { ... }
}

class A: Base {}
class B: Base {}
class C: Base {}

let classes = [A.self, B.self, A.self, B.self, C.self]
for cls in classes {
    let obj = ???
}

I would like to instantiate an object of type cls inside the loop and do something with it. I might have duplicates inside the array, as shown. What do I put in place of the ??? to be able to instantiate the proper objects?

Answer 1

All you need is a required init, some way to create an instance that will be shared between all Types you want this to work for. A protocol that holds an init method will do fine.

Obviously this works simplest when the init does not require parameters.

Downside is that you do need to downcast the resulting instances.

protocol ZeroParamaterInit {
    init()
}

class Base : ZeroParamaterInit {
    func launch(code1: Int, code2: Int) {  }
    required init() {

    }
}

class A: Base {}
class B: Base {}
class C: Base {}

let classes : [ZeroParamaterInit.Type] = [A.self,B.self]
var instances : [Any] = []

for cls in classes {

    let instance = cls.init()
    instances.append(instance)

}

for instance in instances {

    if let test = instance as? A {
        print("A")
    }
    if let test = instance as? B {
        print("B")
    }
    if let test = instance as? C {
        print("C")
    }
}