Feature Envy

Feature envy reveals a method (or method-to-be) that would work better on a different class.

Symptoms

• Repeated references to the same object.
• Parameters or local variables which are used more than methods and instance variables of the class in question.
• Methods that includes a class name in their own names (such as invite_user).
• Private methods on the same class that accept the same parameter.
• Law of Demeter violations.
• Tell, Don’t Ask violations.

Solutions

• Extract Method⭐ if only part of the method suffers from feature envy, and then move the method.
• Move Method⭐ if the entire method suffers from feature envy.
• Inline Class if the envied class isn’t pulling its weight.

Prevention

• Follow Law of Demeter ⇒ limit the dependencies of each method.
• Follow Tell, Don’t Ask ⇒ avoiding unnecessary inspection of another object’s state.