Set type of an array when initializing a class

Question

I have a class called Controller that contains one Array property. Right now, my class is declared like that:

class Controller {
    var myArray: [AnyObject] 

    init(bool: Bool) {
        if bool == true {
            myArray = [10, 11, 12]
        } else {
            myArray = ["Yo", "Ya", "Yi"]
        }
    }
}

The problem that I have with this code is that myArray is still (of course) of type [AnyObject] after my class initialization. Thus, every time I need to get an object out of myArray, I have to cast its type (Int or String) just like this:

let controller = Controller(bool: false)
let str = controller.array[0] as String

I want to be able to write let str = controller.array[0] //str: String without having to cast the real type of the objects inside myArray. Is there a way to do so? Do I have to use lazy init, struct, generic types?

Here is a attempt in pseudo code:

class Controller {
    var myArray: Array<T> //Error: use of undeclared type 'T'

    init(bool: Bool) {
        if bool == true {
            myArray = [10, 11, 12] as [Int] //myArray: Array<Int>
        } else {
            myArray = ["Yo", "Ya", "Yi"] as [String] //myArray: Array<String>
        }
    }
}

Why does your array need to contain variant types at run time? Is this something you could design around? It seems very confusing, I would be thrown by this if I were to jump into the code base. — Chris Wagner
– Chris Wagner, Commented Aug 4, 2014 at 16:45

Chris Wagner · Accepted Answer · 2014-08-04 20:15:11Z

3

So as Oscar and Elijah pointed out (up votes to them), I am just trying to be a little more verbose here. You need to declare the generic, T, when you define the class.

This would mean you need to define what that generic's type is at initialization of the class.

class Foo<T> {
    var items = [T]()
}

let stringFoo = Foo<String>()

stringFoo.items.append("bar")
stringFoo.items[0] = "barbar"

stringFoo.items                 // ["barbar"]



let intFoo = Foo<Int>()

intFoo.items.append(1)
intFoo.items[0] = 11

intFoo.items                    // [11]

So in your case, rather than passing a Bool for the init method, just define the generic's type at initialization instead.

answered Aug 4, 2014 at 20:15

Chris Wagner

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Elijah Igny · Accepted Answer · 2014-08-04 17:14:21Z

3

class Controller<T> //You missed that T, right?
{ 
    var myArray: Array<T>
    /* initialization stuff */
}

var c = Controller<String>()
c.myArray[0] = "Hey!"
let str = c.myArray[0] //String, eventually!

answered Aug 4, 2014 at 17:14

Elijah Igny

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Oscar Swanros · Accepted Answer · 2014-08-04 18:42:00Z

2

class Controller<T> {
    var array: Array<T> = []

    ...
}

answered Aug 4, 2014 at 18:42

Oscar Swanros

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1 Comment

ChiefTwoPencils Over a year ago

You can't add a little dialog to this?

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