Data commit

Task/Singleton/OoRexx/singleton.rexx

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+a = .singleton~new
+b = .singleton~new
+
+a~foo = "Rick"
+if a~foo \== b~foo then say "A and B are not the same object"
+
+::class singleton
+-- initialization method for the class
+::method init class
+  expose singleton
+  -- mark this as unallocated.  We could also just allocate
+  -- the singleton now, but better practice is probably wait
+  -- until it is requested
+  singleton = .nil
+
+-- override the new method.  Since this is a guarded
+-- method by default, this is thread safe
+::method new class
+  expose singleton
+  -- first request?  Do the real creation now
+  if singleton == .nil then do
+     -- forward to the super class.  We use this form of
+     -- FORWARD rather than explicit call ~new:super because
+     -- this takes care of any arguments passed to NEW as well.
+     forward class(super) continue
+     singleton = result
+  end
+  return singleton
+
+-- an attribute that can be used to demonstrate this really is
+a singleton.
+::attribute foo