Make class iterable with for for for Loop?

You should take a look at this blog post on this exact topic. I'll write his summary here:

When you write:

// mySequence is a type that conforms to the SequenceType protocol.
for x in mySequence {
    // iterations here
}

      

        
        
        
      

    

Swift converts this value to:

var __g: Generator = mySequence.generate()
while let x = __g.next() {
    // iterations here
}

      

        
        
        
      

    

Therefore, in order to be able to enumerate your custom type, you need to force your class to implement the protocol SequenceType

. If you look at the SequenceType

protocol below, you can see that you only need to implement one method that returns an object corresponding to the protocol GeneratorType

( GeneratorType

included in the blog post).

protocol SequenceType : _Sequence_Type {
    typealias Generator : GeneratorType
    func generate() -> Generator
}

      

        
        
        
      

    

Here's an example of how to make it MyArrayClass

useful in a loop for

:

class MyArrayClass {
    var array: [String] = []

    func append(str: String) {
        array.append(str)
    }
}

extension MyArrayClass : SequenceType {
    // IndexingGenerator conforms to the GeneratorType protocol.
    func generate() -> IndexingGenerator<Array<String>> {
        // Because Array already conforms to SequenceType,
        // you can just return the Generator created by your array.
        return array.generate()
    }
}

      

        
        
        
      

    

Now, to put this into practice:

let arr = MyArrayClass()
arr.append("first")
arr.append("second")
arr.append("third")

for x in arr {
    println(x)
}

// Prints:
//     First
//     Second
//     Third

      

        
        
        
      

    

Hope that's the answer to your question.