September 2017 Update

Task/Add-a-variable-to-a-class-instance-at-runtime/OoRexx/add-a-variable-to-a-class-instance-at-runtime-1.rexx

@@ -0,0 +1,37 @@
+d = .dynamicvar~new
+d~foo = 123
+say d~foo
+
+d2 = .dynamicvar2~new
+d~bar = "Fred"
+say d~bar
+
+-- a class that allows dynamic variables.  Since this is a mixin, this
+-- capability can be added to any class using multiple inheritance
+::class dynamicvar MIXINCLASS object
+::method init
+  expose variables
+  variables = .directory~new
+
+-- the UNKNOWN method is invoked for all unknown messages.  We turn this
+-- into either an assignment or a retrieval for the desired item
+::method unknown
+  expose variables
+  use strict arg messageName, arguments
+
+  -- assignment messages end with '=', which tells us what to do
+  if messageName~right(1) == '=' then do
+     variables[messageName~left(messageName~length - 1)] = arguments[1]
+  end
+  else do
+      return variables[messageName]
+  end
+
+
+-- this class is not a direct subclass of dynamicvar, but mixes in the
+-- functionality using multiple inheritance
+::class dynamicvar2 inherit dynamicvar
+::method init
+  -- mixin init methods are not automatically invoked, so we must
+  -- explicitly invoke this
+  self~init:.dynamicvar

Task/Add-a-variable-to-a-class-instance-at-runtime/OoRexx/add-a-variable-to-a-class-instance-at-runtime-2.rexx

@@ -0,0 +1,35 @@
+d = .dynamicvar~new
+d~foo = 123
+say d~foo
+
+-- a class that allows dynamic variables.  Since this is a mixin, this
+-- capability can be added to any class using multiple inheritance
+::class dynamicvar MIXINCLASS object
+::method init
+  expose variables
+  variables = .directory~new
+
+-- the unknown method will get invoked any time an unknown method is
+-- used.  This UNKNOWN method will add attribute methods for the given
+-- name that will be available on all subsequent uses.
+::method unknown
+  expose variables
+  use strict arg messageName, arguments
+
+  -- check for an assignment or fetch, and get the proper
+  -- method name
+  if messageName~right(1) == '=' then do
+     variableName = messageName~left(messageName~length - 1)
+  end
+  else do
+     variableName = messageName
+  end
+
+  -- define a pair of methods to set and retrieve the instance variable.  These are
+  -- created at the object scope
+  self~setMethod(variableName, 'expose' variableName'; return' variableName)
+  self~setMethod(variableName'=', 'expose' variableName'; use strict arg value;' variableName '= value' )
+
+  -- reinvoke the original message.  This will now go to the dynamically added
+  methods
+  forward to(self) message(messageName) arguments(arguments)