Moving Features between Objects

Even if you have distributed functionality among different classes in a less-than-perfect way, there is still hope.

These refactoring techniques show how to safely move functionality between classes, create new classes, and hide implementation details from public access.

Move Method

Problem: A method is used more in another class than in its own class.

Solution: Create a new method in the class that uses the method the most, then move code from the old method to there. Turn the code of the original method into a reference to the new method in the other class or else remove it entirely.

Move Field

Problem: A field is used more in another class than in its own class.

Solution: Create a field in a new class and redirect all users of the old field to it.

Extract Class

Problem: When one class does the work of two, awkwardness results.

Solution: Instead, create a new class and place the fields and methods responsible for the relevant functionality in it.

Inline Class

Problem: A class does almost nothing and is not responsible for anything, and no additional responsibilities are planned for it.

Solution: Solution: Move all features from the class to another one.

Hide Delegate

Problem: The client gets object B from a field or method of object А. Then the client calls a method of object B.

Solution: Create a new method in class A that delegates the call to object B. Now the client does not know about, or depend on, class B.

Remove Middle Man

Problem: A class has too many methods that simply delegate to other objects.

Solution: Delete these methods and force the client to call the end methods directly.

Introduce Foreign Method

Problem: A utility class does not contain the method that you need and you cannot add the method to the class.

Solution: Add the method to a client class and pass an object of the utility class to it as an argument.

Introduce Local Extension

Problem: A utility class does not contain some methods that you need. But you cannot add these methods to the class.

Solution: Create a new class containing the methods and make it either the child or wrapper of the utility class.