Control coupling occurs when a method or block checks the value of a parameter in order to decide which execution path to take. The offending parameter is often called a Control Couple.
Control Coupling is a kind of duplication, because the calling method already knows which path should be taken.
Control Coupling reduces the code's flexibility by creating a dependency between the caller and callee: any change to the possible values of the controlling parameter must be reflected on both sides of the call. A Control Couple also reveals a loss of simplicity: the called method probably has more than one responsibility, because it includes at least two different code paths.
You can find a good write-up regarding this problem here.
Reek performs the following checks that fall in this category:
- Control-Parameter - a method parameter or block parameter is the tested value in a conditional statement
- Boolean-Parameter - a method parameter is defaulted
to
trueorfalse.