Anti Pattern: Multiple Purposes for the same method

As I continue in my adventure of product support, I have come across some more anti-patterns that I would like to share with the community at large.


In a previous blog, we talked about the anti-pattern of partially filled objects.  Another horrendous anti-pattern is defining a method that tries to be multi-purpose.  This brings me to my next set of rules.


1. DO NOT Define a Method that does more than one well-defined task.

1a.  Do not define a function that does completely opposite tasks in the same method

1b.  Do not pass  a boolean or any other parameter into a method that flags the method to behave completely differently than it was intended.

Let me give an example.  Let's take the following method


void LoadProject (bool save)
{
// load the project into the project class
   if (save == false)
      GetProjectFromDatabase();

   if (save == true)
    {
      SaveTheProject(_currentProject)
    }

}

The fact that this project is doing two completely different tasks breaks the main rule #1.    Since the method is accepting a boolean that changes the intended behavior of the method,  this part of the definition breaks rule 1a and 1b.

You may think I'm making this up, but I just came across this in code, and I've even seen it before in some older standard libraries.

Correct Behavior

How should this method be refactored to defeat this scary anti-pattern?  If we just think about rule #1, we can quickly come up with a solution.  Simply divide the method into two well defined tasks and name them appropriately

void LoadProject()
{
   GetProjectFromTheDatabase();
}

void SaveProject()
{
   SaveTheProject(_currentProject);
}

Now it is very clear to other programmers looking at your code what each method is doing.  Rule #1 is based on the basic CS concept of high cohesion