Open Radar

 
Summary:
Discussion on the developer forums indicated that the recommended singleton pattern in Swift is to simply declare a class constant, and, if the object might be encoded using NSCoding, use awakeAfterUsingCoder to replace it:

    class Foo {
        class let sharedFoo = Foo()    // once class vars are supported; there are getter-based workarounds too
        
        func awakeAfterUsingCoder(aDecoder: NSCoder!) -> AnyObject! {
            return Foo.sharedFoo
        }
    }

This pattern is not discussed in any documentation. I believe it should be.

Steps to Reproduce:
1. Search “The Swift Programming Language” for the word “singleton”.

Expected Results:
A section discussing how singletons should be implemented in Swift, and how this pattern may or may not differ from Objective-C’s techniques.

Actual Results:
No such section is included.

Notes:
I’m not a huge fan of allowing multiple instances of a singleton to be allocated in any way, but the pattern mentioned above is at least acceptable. However, it’s not an obvious thing to do, and it’d be helpful if the documentation pointed it out.