- Duplicated Code
- Long Method
- Large Class
- Long Parameter List
- Divergent Change
- Shotgun Surgery
- Feature Envy
- Data Clumps
- Primitive Obsession
- Case Statements
- Parallel Inheritance Hierarchies
- Lazy Class
- Speculative Generality
- Temporary Field
- Message Chains
- Middle Man
- Inappropriate Intimacy
- Alternative Classes with Different Interfaces
- Incomplete Library Class
- Data Class
- Refused Bequest
- Comments
- Metaprogramming Madness
- Disjointed API
- Repetitive Boilerplate
This chapter is from the book
This chapter is from the book
This chapter is from the book
Middle Man
One of the prime features of objects is encapsulation—hiding internal details from the rest of the world. Encapsulation often comes with delegation. You ask a director whether she is free for a meeting; she delegates the message to her diary and gives you an answer. All well and good. There is no need to know whether the director uses a diary, an electronic gizmo, or a secretary to keep track of her appointments.
However, this can go too far. You look at a class's interface and find half the methods are delegating to this other class. After a while it is time to use Remove Middle Man and talk to the object that really knows what's going on. If only a few methods aren't doing much, use Inline Method to inline them into the caller. If there is additional behavior, you can use Replace Delegation with Hierarchy to turn the real object into a module and include it in the middle man. That allows you to extend behavior without chasing all that delegation.