Design Patterns Một mẫu thiết kế bao gồm một hoặc nhiều đối tượng cùng nhau thực hiện một số nhiệm vụ hữu ích. Trong một nghĩa nào đó, một mẫu thiết kế là một thuật toán cho việc sử dụng các lớp học để làm một cái gì đó hữu ích. Đó là một công thức để xây dựng một phần của một ứng dụng. Một mẫu thiết kế có thể bao gồm các đối tượng từ một lớp học duy nhất, hoặc một bộ quần áo đồng bộ của các lớp học làm việc cùng nhau. Khi bạn tinh. | Design Patterns A design pattern consists of one or more objects that together perform some useful task. In a sense a design pattern is an algorithm for using classes to do something useful. It s a recipe for building part of an application. A design pattern may include objects from a single class or an ensemble of classes working together. As you refine your application s design you should start looking for common design patterns. You may discover a group of classes that implement a pattern. You may also find a group of classes that you could rewrite to follow a pattern. In either case if you can rewrite your design to follow a design pattern then you can take advantage of the solutions that other developers have developed to solve the same problem. That can save you time and gives you some confidence that the solution will work correctly so you can move on to design other parts of the application. Some patterns also make an application easier to implement debug and maintain. For example the Adapter and Facade patterns described later in this chapter help decouple classes so they are less tightly related. That lets you build debug and modify the classes with less impact on the rest of the application. Since the seminal book Design Patterns by Gamma et. al Boston Addison-Wesley 1995 was published all sorts of patterns have been devised for data access integration interoperability services security Web Services configuration exceptions testing threat modeling legacy applications project management and many more. This chapter or even this whole book doesn t have room to cover them all. Rather than just listing the names of a bunch of design patterns with no explanation this chapter describes in more detail some of the patterns that I have found most useful in the applications that I ve built. A lot of the design pattern books treat their patterns in a very formal way with introductory sections for each pattern giving a synopsis context forces and other sections .
