1、尽量使用聚合或者组合,尽量不使用类继承。对象的继承关系是在编译时就定义好的,所以无法在运行时改变从父类继承的实现 。子类的实现与它的父类有着非常紧密的依赖关系,以至于父类实现中的任何变化必然会导致子类发生变化。当需要复用子类时,如果集成下来的实现不符合解决新的问题,则父类必然重写或被其他更合适的类替换。这种依赖关系限制了灵活性并最终限制了复用性。二、解决的问题(What To Solve) 当系统有多维角度分类时,而每一种分类又有可能变化,这时考虑使用桥接模式比较合适。三、桥接模式分析(Analysis)1、桥接模式结构Abstraction类:业务抽象类,定义一个抽象接口,维护对Impeme
2、ntor的引用.RefinedAbstraction类:具体实现类,被提炼的抽象Implementor类:定义一个抽象实现类,此抽象类与Abstraction类不一定完全相同。Implementor类提供了一些原始的操作,而Abstraction类是对这些原始操作一个更高层次的封装.ConcreteImplementorA,ConcreteImplementorA类:具体实现2、代码1、业务抽象类Abstraction及其提炼出的具体实现类RefinedAbstractionpublic abstract class Abstraction protected Implementor _imp
3、lementor; public Implementor Implementor set _implementor = value; get return _implementor; public virtual void Operation() _implementor.OperationImp();public class RefinedAbstraction:Abstraction public override void Operation()2、抽象实现类Implementor 及其具体实现类ConcreteImplementorA和ConcreteImplementorBpubli
4、c abstract class Implementor public abstract void OperationImp();public class ConcreteImplementorA:Implementor public override void OperationImp() Console.WriteLine(0 Operation Method,this.GetType().Name);public class ConcreteImplementorB:, this.GetType().Name);2、客户端代码static void Main(string args) A
5、bstraction a1 = new RefinedAbstraction(); / Set implementation and call a1.Implementor = new ConcreteImplementorA(); a1.Operation(); / Change implemention and call a1.Implementor = new ConcreteImplementorB(); Console.ReadKey();3、实例运行结果四桥接模式实例分析(Example)1、场景业务对象(BusinessObject)与数据对象(DataObject)分离,即业务
6、对象CustormerBase与数据对象DataObject分离。业务对象CustormerBase完成更高层次的业务操作。结构如下图所示CustomersBasel类:定义一个抽象接口,维护对DataObject的引用。Custorers类:被提炼的抽象。DataObject类:数据抽象类主要操作有添加纪录。删除纪录、定位Next纪录、定位Prior纪录,展示所有纪录,展示当前纪录等。CustomersData类:数据抽象类的具体实现。1、抽象接口CustomersBase及其具体实现类Customersclass CustomersBase private DataObject _data
7、Object; protected string group; public CustomersBase(string group) this.group = group; / Property public DataObject Data set _dataObject = value; get return _dataObject; public virtual void Next() _dataObject.NextRecord(); public virtual void Prior() _dataObject.PriorRecord(); public virtual void Ad
8、d(string customer) _dataObject.AddRecord(customer); public virtual void Delete(string customer) _dataObject.DeleteRecord(customer); public virtual void Show() _dataObject.ShowRecord(); public virtual void ShowAll()Customer Group: + group); _dataObject.ShowAllRecords();/ / The RefinedAbstraction clas
9、s/summaryclass Customers : CustomersBase / Constructor public Customers(string group) : base(group) public override void ShowAll() / Add separator lines Console.WriteLine();*); base.ShowAll();2、抽象数据对象类DataObject及其具体实现类CustomersDataabstract class DataObject public abstract void NextRecord(); public a
10、bstract void PriorRecord(); public abstract void AddRecord(string name); public abstract void DeleteRecord(string name); public abstract void ShowRecord(); public abstract void ShowAllRecords();ConcreteImplementorclass CustomersData : DataObject private List _customers = new List(); private int _cur
11、rent = 0; public CustomersData() / Loaded from a database _customers.Add(James Hao灵动生活郝*宪*玮 public override void NextRecord() if (_current 0) _current-; public override void AddRecord(string customer) _customers.Add(customer); public override void DeleteRecord(string customer) _customers.Remove(cust
12、omer); public override void ShowRecord() Console.WriteLine(_customers_current); public override void ShowAllRecords() foreach (string customer in _customers) + customer);3、客户端代码 / Create RefinedAbstraction CustomersBase customers = new Customers(Shandong Province / Set ConcreteImplementor customers.Data = new CustomersData(); / Exercise the bridge customers.Show(); customers.Next(); customers.Add(Hao xianwei customers.ShowAll();五、总结(Summary)本文对桥接模式(Bridge Pattern)的概念、设计结构图、代码、使用场景、聚合与合成原则以及什么是聚合/合成进行了描述。以一个桥接模式实例进行了说明。桥接模式是比较常用和简单的设计模式。当系统有多维角度分类时,而每一种分类又有可能变化,可以考虑使用桥接模式。
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