Converting strings in to arrays

ArrayExtension

import Foundation

extension Array: StringLiteralConvertible {
    init(string: String) {
        self.init()
        appendContentsOf(string.componentsSeparatedByString(",").flatMap {
            switch Element.self {
                case is Int.Type:
                    return Int($0) as? Element
                case is Double.Type, is Float.Type:
                    return Double($0) as? Element
            default:
                return $0 as? Element
            }
        })
    }
    
    public typealias ExtendedGraphemeClusterLiteralType = String
    public typealias UnicodeScalarLiteralType = String
    
    public init(stringLiteral value: StringLiteralType){
        self.init(string: value)
    }
    
    public init(extendedGraphemeClusterLiteral value: ExtendedGraphemeClusterLiteralType){
        self.init(string: value)
    }
    
    public init(unicodeScalarLiteral value: UnicodeScalarLiteralType){
        self.init(string: value)
    }
}

let a: Array<String> = "1,2,3" // ["1", "2", "3"]
let b: Array<Int> = "1,2,3" // [1, 2, 3]
let c: Array<Double> = "1.5,2.0,foo,3.1" // [1.5, 2.0, 3.1]