Class LazyAction

source code

        object --+        
                 |        
        ActionBase --+    
                     |    
CommandGeneratorAction --+
                         |
    object --+           |
             |           |
    ActionBase --+       |
                 |       |
     _ActionAction --+   |
                     |   |
         CommandAction --+
                         |
                        LazyAction

A LazyAction is a kind of hybrid generator and command action for strings of the form "$VAR". These strings normally expand to other strings (think "$CCCOM" to "$CC -c -o $TARGET $SOURCE"), but we also want to be able to replace them with functions in the construction environment. Consequently, we want lazy evaluation and creation of an Action in the case of the function, but that's overkill in the more normal case of expansion to other strings.

So we do this with a subclass that's both a generator and a command action. The overridden methods all do a quick check of the construction variable, and if it's a string we just call the corresponding CommandAction method to do the heavy lifting. If not, then we call the same-named CommandGeneratorAction method. The CommandGeneratorAction methods work by using the overridden _generate() method, that is, our own way of handling "generation" of an action based on what's in the construction variable.