Program to an interface, not an implementation
Don't declare variables to be instances of particular concrete classes. Instead, commit only to an interface defined by an abstract class (查看原文)
This dependency limits flexibility and ultimately reusability. One cure for this is to inherit only from abstract classes, since they usually provide little or no implementation. (查看原文)
Avoid coupling the sender of a request to its receiver by giving more than one object a chance to handle the request. Chain the receivingobjects and pass the
request along the chain until an object handles it. (查看原文)
1. Reduced coupling.The pattern frees an object from knowing which other object handles arequest. An object only has to know that a request will be
handled"appropriately." Both the receiver and the sender have no explicit knowledge of each other, and an object in the chain doesn't have to know about the chain's structure.
As a result, Chain of Responsibility can simplify object interconnections. Instead of objects maintaining references to all candidate receivers, they keep a single reference to their successor.
2. Added flexibility in assigning responsibilities to objects.Chain of Responsibility gives you added flexibility in distributing responsibilities among objects. You can add or
change responsibilities for handling a request by adding to or otherwise changing the chain at run-time. ... (查看原文)
Factory methods in C++ are always virtual functions and are often pure virtual. Just be careful not to call factory methods in the Creator's constructor—the factory method in the ConcreteCreator won't be available yet. (查看原文)
