Swift var type for class - swift

Question

I have the next example where I have a problem to initialize the variable tmpClass, I tried Any, AnyObject, AnyClass ... but without success. I need to change and call the class dynamically from one variable
class One{
func doSomething()->Int{ return 100 }
}
class Two{
func doSomething()->Int{ return 200 }
}
class begin{
var tmpClass = ???
var type = "One"
switch (type){
case "One":
tmpClass = One()
case "Two":
tmpClass = Two()
}
println(tmpClass.doSomething())
}
the question is what type need to be tmpClass or some method to do that ?

Answer 1

You can do it in two different ways, see which fits you better:
Protocols
Create a protocol for doSomething
protocol DoSomethingProtocol {
func doSomething()->Int
}
Make your classes conform to it
class One : DoSomethingProtocol {
func doSomething()->Int{ return 100 }
}
class Two : DoSomethingProtocol{
func doSomething()->Int{ return 200 }
}
Set your tempClass variable to be of a protocol compliant class
var tmpClass: DoSomethingProtocol?
Inheritance
Create a base class with the doSomething method
class DoSomethingBaseClass {
func doSomething()->Int{ return 0 }
}
Override doSomething in your classes
class One : DoSomethingBaseClass {
override func doSomething()->Int{ return 100 }
}
class Two : DoSomethingBaseClass{
override func doSomething()->Int{ return 200 }
}
Set your tempClass variable to be of the super class (polymorphism!)
var tmpClass: DoSomethingBaseClass?
General tips
In Swift switches must be exhaustive (all possible options must have a case), to fix this in your example you can simply add
default:
tmpClass = nil
Do not forget to unwrap your optional. For safety you can use the if let syntax for optional binding:
if let tmpUnwrappedClass = tmpClass {
println(tmpUnwrappedClass.doSomething())
}
You could just use the ! unwrap operator as in println(tmpClass!.doSomething()) but this will fail when tmpClass is nil.
Your begin class has two properties and no initializers. Classes with properties must have a designated initializer to set them, that's why I removed the whole class.
Both versions are tested and working in the latest Swift using Playground.