CheckDoSomething()

I have gotten a lot of use out of what I might call the Check Execute Method pattern. The general idea is that, often times, you want to conditionally execute some action. For example, you may have something like the following appear in several different places:

if condition
  doSomething()
end

If you're not careful, code like this may get sprinkled all over the place. If many callers are checking the same condition, we can DRY up the code as follows:

def checkDoSomething(condition)
  if condition
    doSomething()
  end

  return condition
end

Now we have encapsulated the decision of whether to execute the method. We no longer need to repeat the check everywhere. The 'check' prefix in the method name makes it clear that the execution of the action is dependent on the parameters or state of the object. Additionally, if the caller needs to know whether or not the action was performed, they can use the boolean return value.

Some may disagree with returning a success value, claiming that this violates command query separation. Fine, but what is the alternative? We could rely on the caller to check some condition before calling the method, but this is problematic if we have more than a few callers who are all checking the same thing. A caller may even forget to make the check.

Alternatively, we could change the method to do the check internally and throw an exception if the condition is not met. But then we're using exceptions for control flow, and each caller would need to wrap the method call in a try-catch block.

There are trade-offs to be made, but I think this approach strikes a nice balance.