Returning command instance from ICommandMap.execute()

Aaron Hardy's Avatar

Aaron Hardy

12 Feb, 2011 09:44 PM

Hey folks,

I've been doing a bit of work on the Macrobot extension ( and came across a need for ICommandMap to return the executed command instance from its execute() function. This arises out of the need for a macro command to track asynchronous subcommand completion. The method employed within Macrobot is that an asynchronous command has a dispatchComplete() method which not only releases the command from memory but marks itself complete and calls any registered listeners. The sequence command can register to be notified when the subcommand completes. When the subcommand notifies the sequence command that it has completed execution, the sequence command can execute the next subcommand in the sequence.

Previously, the macro commands were completely in charge of fulfilling injections into subcommands as well as execution. This worked fine but you lose the benefits of having a single point of command execution through a context's command map. In one case, I wanted to add logging capabilities to my context's command map to record when any command was executed. However, since macro commands directly handled the execution of subcommands, the command map would not know about it and therefore the subcommand's execution would never be logged.

So, for Macrobot I created an optional IMacroCommandMap interface and concrete implementation that allows macro commands to use the IMacroCommandMap to execute any subcommands. This allows for a single point of command execution as I described previously. If ICommandMap returned the command on execute, the macro command could first check to see if the subcommand is already complete (which could happen if an AsyncCommand immediately dispatches completion, that is, it's not really asynchronous) and, if it's not already complete, add a completion listener to the instance.

You may feel a bit queezy making this modification as returning the command instance could introduce some coupling issues if developers chose to mis-use it (maybe I'm one of those). If that's the case, no problem. I just thought I'd throw it out there in case it could be useful for other extensions as well. At least for Macrobot, it would do away with the need for implementing a custom command map.

In addition, if I'm on the wrong track and you see a better way to handle the macro command scenario, please, let me know. Thanks!

  1. Support Staff 1 Posted by Stray on 13 Feb, 2011 04:45 PM

    Stray's Avatar

    Hi Aaron, unfortunately changing the return type of a function is a breaking change - so we can't do it in RL 1.x because of semantic versioning.

    Any utility / code that implements ICommandMap or extends CommandMap would have to be altered to match the new return type, so it's no dice for now.

    I'll put it on the 2.0 list for consideration though,


  2. Stray closed this discussion on 13 Feb, 2011 04:45 PM.

  3. Stray re-opened this discussion on 13 Feb, 2011 04:46 PM

  4. 2 Posted by Aaron Hardy on 13 Feb, 2011 05:10 PM

    Aaron Hardy's Avatar

    Understood. Thanks.

  5. Stray closed this discussion on 19 Feb, 2011 06:19 PM.

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