NSObject class conforms to protocol contained in NSArray with Swift

Question

I would like to create a method in Swift that returns an array of NSObject objects that conform to a protocol. I've tried something like this:

func createManagers() -> [Manager] {
    let result = NSMutableArray(capacity: self.classes.count)
    (self.classes as NSArray).enumerateObjectsUsingBlock { (object: AnyObject!, idx: Int, stop: UnsafeMutablePointer<ObjCBool>) -> Void in
        // TODO: do something and fill the result array
    }
    return result as NSArray as! [Manager]
}

Manager is a protocol as you see. I am receiving the error that the cast at the return statement will always fail.
I want to tell the compiler that I have an array of objects of NSObject type and all elements conform to Manager protocol.

score 1 · Accepted Answer · answered Jun 17 '15 at 16:15

1

Don't try to write Objective-C in Swift. Move away from NSObject, NSArray and NSMutableArray.

Here is your code without any Objective-C types:

func createManagers() -> [Manager] {
    let result = [Manager]()
    for (index, aClass) in classes.enumerate() {
        // TODO: do something and fill the result array
    }
    return result
}

If you want to ensure your return types are a subclass of NSObject:

func createManagers<T: NSObject where T: Manager>() -> [T] {
    var result = [T]()
    for (index, aClass) in classes.enumerate() {
        // TODO: do something and fill the result array
    }
    return result
}

answered Jun 17 '15 at 16:15

vrwim

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, can you please point me to the documentation where I can read more about this? Thank you! – Infinite Possibilities Jun 18 '15 at 11:29
1

[here](https://developer.apple.com/library/mac/documentation/Swift/Conceptual/Swift_Programming_Language/Generics.html) is the documentation on Swift generics. – vrwim Jun 18 '15 at 11:32

score 0 · Answer 2 · answered Jun 16 '15 at 08:21

0

Your return type is a Dictionary with key NSObject and value type Manager, instead of an array. Change the return type to [Manager]. Also you probably want to use the map function of array:

func createManagers() -> [Manager] {
    return classes.map { doSomethingAndTransformIntoManager($0) }
}

answered Jun 16 '15 at 08:21

lammert

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Ok, I am going to edit my question. This is the one I've tried for the first time, but this doesn't work. I want to tell the compiler that I have an array of objects of NSObject type and all elements conform to Manager protocol. – Infinite Possibilities Jun 16 '15 at 08:23

NSObject class conforms to protocol contained in NSArray with Swift

2 Answers2