设计模式 - 组合模式

• 组合模式
  将对象组合成树形结构以表示"部分-整体"的层次结构。组合模式是的用户对单个对象和组合对象的使用具有一致性。

//对象的声明接口
abstract class Component
{
    protected string name;
    public Component(string name)
    {
        this.name = name;
    }
    public abstract void Add(Component c);
    public abstract void Remove(Component c);
    public abstract void Display(int depth);
}
//叶子
class Leaf:Component
{
    public Leaf(string name)
    :base(name)
    {}
    public override void Add(Component c)
    {
        Console.WriteLine("Cannot add to a leaf");
    }
        public override void Remove(Component c)
    {
        Console.WriteLine("Cannot Remove from a leaf");
    }

    public override void Display(int depth)
    {
        Console.WriteLine(new String('-',depth)+name);
    }
}
//树枝
class Composite:Component
{
    //1.声明组件数组
    private List<Component>children = new List<Component>();
    public Component(string name)
    :base(name)
    {}

    public override void Add(Component c){
        children.Add(c);
    }

    public override void Remove(Component c){
        children.Remove(c);
    }

    public override void Display(int depth)
    {
        Console.WriteLine(new String('-',depth) + name);
        foreach (Component component in children)
        {
            component.Display(depth + 2);
        }
    }
}
//客户端调用
static void Main(string[] args)
{
    //1.声明主干组件,并添加两个叶子
    Composite root = new Composite("root");
    root.Add(new Leaf("Leaf A"));
    root.Add(new Leaf("Leaf B"));
    //2.添加分支,并给分支添加叶子，将分支添加到主干上
    Composite comp = new Composite("Composite X");
    comp.Add(new Leaf("Leaf XA"));
    comp.Add(new Leaf("Leaf XB"));
    root.Add(comp);
    //3.添加分支,并给分支添加叶子，将分支添加到主干上
    Composite comp2 = new Composite("Composite XY");
    comp2.Add(new Leaf("Leaf XYA"));
    comp2.Add(new Leaf("Leaf XYB"));
    root.Add(comp2);
    //显示总的样式
    root.Display(1);
    Console.Read();
}

• 透明方式与安全方式

  • 透明模式：叶节点与枝节点对于外界是没有分别的，它们具备对外一致的接口。但是问题也是很明显，因为Leaf 类本身不具备 Add(),Remove() 方法的功能，所以实现它是没有意义的。
  • 安全模式：Component 接口中不去声明 Add() 和 Remove() 方法，那么子类的 Leaf 就不需要去实现它，而是在 Composite 声明所有用来管理子类对象的方法，不过由于不够透明，所以树叶和树枝类将不具有相同的接口。客户端的调用需要相应的判断，带来的不便。

• 实际应用

abstract class Company
{
    protected string name;
    public Company(string name)
    {
        this.name = name;
    }
    public abstract void Add(Company c);//添加
    public abstract void Remove(Company c);//减少
    public abstract void Display(Company c);//展示
    public abstract void LineOfDuty();//履行职责
}
class ConcreteCompany : Company
{
    private List<Company>children = new List<Company>();
    public ConcreteCompany(string name):base(name)
    {}
    public override void Add(Company c){
        children.Add(c);
    }
    public override void Remove(Company c)
    {
        children.Remove(c);
    }
    public override void Display(int depth)
    {
        Console.WriteLine(new string('-',depth)+name);
        foreach (Company component in children)
        {
            component.Display(depth + 2);
        }
    }
    public override void LineOfDuty()
    {
        foreach(Company component in children)
        {
            component.LineOfDuty();
        }
    }
}
class HRDepartment : Company
{
    public HRDepartment(string name):base(name){}
    public override void Add(Company c){
    }
    public override void Remove(Company c)
    ｛｝
    public override void Display()
    {
        Console.WriteLine(new String('-',depth) + name);
    }
    public override void LineOfDuty()
    {
        Console.WriteLine("{0}",name);
    }
}
class FinanceDepartment :Company
{
    public FinanceDepartment(string name):base(name)
    {}
    public override void Add(){}
    public override void Remove(){}
    public override void Display()
    {
        Console.WriteLine(new String('-',depth)+ name);
    }
    public override void LineOfDuty()
    {
        Console.WriteLine("{0}",name);
    }
}
static void Main(string[] args)
{
    ConcreteCompany root = new ConcreteCompany("总公司");
    root.Add(new HRDepartment("hr"));
    root.Add(new FinanceDepartment("Final"));
    ConcreteCompany comp = new ConcreteCompany("上海分公司");
    comp.Add(new HRDepartment("hr"));
    comp.Add(new FinanceDepartment("Final"));
    root.Add(comp);
    ConcreteCompany com1 = new ConcreteCompany("沈阳办事处");
    com1.Add(new HRDepartment("hr"));
    com1.Add(new FinanceDepartment("Final"));
    comp.Add(com1);
    ConcreteCompany com2 = new ConcreteCompany("大连办事处");
    com2.Add(new HRDepartment("hr"));
    com2.Add(new FinanceDepartment("Final"));
    comp.Add(com2);
    Console.WriteLine("\n 结构图:")
        root.Display(1);
    Console.WriteLine("\nDuty:")
        root.LineOfDuty();
    Console.Read();
}