Using a Type Variable in a Generic

Question

I have this question except for Swift. How do I use a Type variable in a generic?

I tried this:

func intType() -> Int.Type {
    retu         


        

Answer 1

jtbandes' answer - that you can't use your current approach because Swift is statically typed - is correct.

However, if you're willing to create a whitelist of allowable types in your array, for example in an enum, you can dynamically initialize different types at runtime.

First, create an enum of allowable types:

enum Types {
    case Int
    case String
}

Create an Example class. Implement your someTypes() function to use these enum values. (You could easily transform a JSON array of strings into an array of this enum.)

class Example {
    func someTypes() -> [Types] {
        var ret = [Types]()
        for _ in 1...rand()%10 {
            if (rand()%2 == 0){ ret.append(.Int) }
            else {ret.append(.String) }
        }
        return ret
    }

Now implement your test function, using switch to scope arr for each allowable type:

    func test() {
        let types = self.someTypes()

        for type in types {
            switch type {
            case .Int:
                var arr = [Int]()
                arr += [4]

            case .String:
                var arr = [String]()
                arr += ["hi"]
            }
        }
    }
}

As you may know, you could alternatively declare arr as [Any] to mix types (the "heterogenous" case in jtbandes' answer):

var arr = [Any]()

for type in types {
    switch type {
    case .Int:
        arr += [4]

    case .String:
        arr += ["hi"]
    }
}

print(arr)