Conditions in Guard

RobotFan's Avatar


25 Mar, 2015 09:56 AM


Firstly, thank you guys for this framework, I love it.

I would like to know, what do you think about more conditions in Guards.
So, what do you think, this approve function is valid and "best practice" or not:

public function approve():Boolean
  return this.carModel.type == "sedan" && this.engineModel.status == "good";

Or I should split it to 2 seperated Guard, like this:

public function approve():Boolean
  return this.carModel.type == "sedan";

public function approve():Boolean
  return this.engineModel.status == "good";

Which is the better? And What should I do, if I have to check the conditions with || and not &&?

  1. Support Staff 1 Posted by Ondina D.F. on 25 Mar, 2015 03:25 PM

    Ondina D.F.'s Avatar

    Hello RobotFan,

    I'm glad to hear that you love robotlegs:)

    Let's take a look at the guardsApprove:
    As you can see, it loops through all the guards, and it returns true only if all the guards returned true.

    If we had a command mapped like this: SomeEvent.SOME_TYPE )
        .toCommand( SomeCommand )
        .withGuards(  FirstGuard, SecondGuard );

    if one of the guards returned false, the command won't be executed.

    So, if you want the command to run on an OR condition, use a single guard

    public function approve():Boolean
        return firstCondition ||  secondCondition;

    Guards are nothing more than a conditional expression that must evaluate to true in order for 'something' to happen (program execution). How you use them, it's up to you.

    If you are always checking for :
    this.carModel.type == "sedan" && this.engineModel.status == "good";
    then one guard would be just fine.

    If you need to use this.carModel.type == "sedan" in one place and this.engineModel.status == "good" somewhere else, and this.carModel.type == "sedan" || this.engineModel.status == "good" yet elsewhere, then maybe 3 guards are required:,, and (for the OR case)

    If you need an AND, as in, you can just add the guards like I did in my example:

    .withGuards( TypeIsSedanGuard, EngineIsGoodGuard );

    Does this clarify your question?


  2. 2 Posted by RobotFan on 26 Mar, 2015 07:52 AM

    RobotFan's Avatar

    Hey Ondina,
    I also thought so, thank you for your confirmation! :)

  3. Support Staff 3 Posted by Ondina D.F. on 28 Mar, 2015 08:58 AM

    Ondina D.F.'s Avatar

    No problem:)

  4. Ondina D.F. closed this discussion on 28 Mar, 2015 08:58 AM.

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