Code refactoring patterns

Comparing a variable to true

If you have code like:

if (variable == true)
{
  // Do action A
}
else
{
  // Do action B
}

You can change this to:

if (variable)
{
  // Do action A
}
else
{
  // Do action B
}

Comparing a variable to false with an else

If you have code like:

if (variable == false)
{
  // Do action A
}
else
{
  // Do action B
}

You can change this to:

if (variable)
{
  // Do action B
}
else
{
  // Do action A
}

Comparing a variable to false without an else

If you have code like:

if (variable == false)
{
  // Do action A
}

You can change this to:

if (!variable)
{
  // Do action A
}

Using a return statement inside an if with an else

If you find code like this:

if (someVariable > 5)
{
   return otherVariable;
}
else
{
  // Lots
  // of
  // other
  // code
  // here
}

You can change this to:

if (someVariable > 5)
{
   return otherVariable;
}
// Lots
// of
// other
// code
// here

This is because there is no danger that the code below the if would be run in the case that the condition is true.

This style of coding is called implementing a guard clause since it protects the code below and provides an early return

Returning a boolean

If you have code like this:

if (variable == true)
{
  return true;
}
else
{
  return false;
}

You can just do:

return variable;

Use a ternary

We can simplify code like the following where we are making a condition and then assigning different values to the same variable.

if (otherVariable == 42)
{
  firstVariable = 17;
}
else
{
  firstVariable = 88;
}

This can be reduced using a ternary

firstVariable = otherVariable == 42 ? 17 : 88;

Creating a variable and only using it once.

In many cases we make a variable to store the result of a computation and then just use it once. In such cases we may want to consider just doing the computation in the place of the variable usage. Other times the presence of the variable makes it easier to read the code by providing context to the value the computation returns. In such cases we should leave the variable.

Example:

var studentsPassingTheClass = students.Where(student => student.homeworkCompletionPercentage > 80);
return studentsPassingTheClass;

could be changed to:

return students.Where(student => student.homeworkCompletionPercentage > 80);