Asier's thoughts

Blogging about software development

Command returns true/false for success/error


I’ve seen this kind of pattern usually when working with web services.

Imaging the following piece of code:

public bool RunCommand()

    // .. Some logic ..

    return true; // success


Basically we have a method in a class that executes some logic, if this is successful it returns a true, if not a false. At first you would say this make sense, right?

It kind of reminds me the days when I was learning C 🙂

But this is just over-complicating things. Any client of this method will have to add a check.

if(RunCommand()) {
  // everything good

  // Show user success message

} else {

  // error!

  // show user something went wrong


Why not just assume that the method is going to be execute successfully? If not just throw and exception! Then just handle that exception. Simple!

Just adding the true/false return for success/error is basically re-implementing exceptions. Well, it’s even worse. Exceptions are explicit, they mean that something went wrong, they even have a custom error message. A boolean just means that.. a boolean: true or false, it’s open to interpretations. When we get a false it could mean anything, no error message, no custom exception.

Also returning values from command methods is a bad practice. You should have two kind of methods: querys that return values but don’t change anything in your system and commands that change something but return nothing! This is known as CQS or Command and Query Separation.


2 thoughts on “Command returns true/false for success/error

  1. I agree that just returning true/false from an endpoint is not great, it doesn’t tell you much. But I’d only rely on exceptions if an error is really exceptional, otherwise my preference would be for a response object to be returned that includes all the relevant information about the results of the endpoint method.

    I hope you’re not advocating wrapping endpoint calls in try / catch blocks? I think that is one of the biggest anti-patterns I commonly come across 😉

  2. Yes, exceptions should be just for exceptional situations. Totally agree! Like if something errors unexpectedly in your application.

    I am not saying that you should throw exceptions to avoid returning true/false. I am just saying that you shouldn’t return anything if you method is a command. The client will just assume that everything is going to work as expected, no need to check for anything extra. Not need of an if-else (like in the example) or try-catches.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s