Design patterns

Editor's Notes

1. One of the overriding principles of object-oriented development is the proper assignment of responsibility in the given application. Each object in the system should focus on a discrete abstraction within the problem domain and nothing more. In short, an object should do one thing and do it well. This approach ensures that a crisp boundary exists between objects, enabling greater reuse and system maintainability. One area where the proper separation of responsibility is of special importance is the interaction between the user interface and the underlying business logic. During the development of an application, it is quite common for user interface requirements to change rapidly without an associated impact on the rest of the application. In addition, it is also likely that the business requirements will change without regard to the user interface. In many cases, both sets of requirements will change, as anyone with substantial development experience well knows. Without the benefit of separation between the UI and remainder of the application, modification of either portion may adversely impact the whole.
2. One of the overriding principles of object-oriented development is the proper assignment of responsibility in the given application. Each object in the system should focus on a discrete abstraction within the problem domain and nothing more. In short, an object should do one thing and do it well. This approach ensures that a crisp boundary exists between objects, enabling greater reuse and system maintainability. One area where the proper separation of responsibility is of special importance is the interaction between the user interface and the underlying business logic. During the development of an application, it is quite common for user interface requirements to change rapidly without an associated impact on the rest of the application. In addition, it is also likely that the business requirements will change without regard to the user interface. In many cases, both sets of requirements will change, as anyone with substantial development experience well knows. Without the benefit of separation between the UI and remainder of the application, modification of either portion may adversely impact the whole.
3. One of the overriding principles of object-oriented development is the proper assignment of responsibility in the given application. Each object in the system should focus on a discrete abstraction within the problem domain and nothing more. In short, an object should do one thing and do it well. This approach ensures that a crisp boundary exists between objects, enabling greater reuse and system maintainability. One area where the proper separation of responsibility is of special importance is the interaction between the user interface and the underlying business logic. During the development of an application, it is quite common for user interface requirements to change rapidly without an associated impact on the rest of the application. In addition, it is also likely that the business requirements will change without regard to the user interface. In many cases, both sets of requirements will change, as anyone with substantial development experience well knows. Without the benefit of separation between the UI and remainder of the application, modification of either portion may adversely impact the whole.
4. Strategy: This is the interface common to all algorithms. Context uses this interface to perform the operations. ConcreteStrategy: This is the class that implements the actual algorithm. Context: This is the client application that performs the decision making for which strategy should be used and uses the Strategy interface (which is referring to a ConcreteStrategy object) to perform the operations.
5. Undo & redo