Swift gotcha with static init

[AndyDentFree]

I'm using a pattern to register the decoding factories that works like this, initialising a static property:

  private static let typeCode = HierCodableFactories.Register(key:"BB") {
    (from) in
    return try? BaseBeast(name:from.read())
  }

However, that's a C++ idiom which is not safe in Swift.

As I found out in my main app's use of this approach, it doesn't work if the first thing you try to do is decode data - none of the factories are registered.

The problem is that the Swift static and class variables are _lazily initialised which means until you refer to them, the closure which does the factory registration is not done.

There are a couple of ways to handle this, cleanest is to move to a separate registration function for all your types and change the typeCode into just a simple assignment. Documenting in this issue because am in shipping hell at present and won't have time to polish this sample for a bit.

Also, thought the issue was an interesting enough gotcha that it deserved a full writeup here for future reference.