《大话设计模式》学习笔记15：组合模式

　　


　　


公司管理系统示例：

　　


1.Component：

public abstract class Company
{
protected string name;
public Company(string name)
{
this.name = name;
}
public abstract void Add(Company company);
public abstract void Remove(Company company);
public abstract void Display(int depth);
public abstract void LineOfDuty();
}

2.Composite：

public class ConcreteCompany:Company
{
private IList<Company> companys = new List<Company>();
public ConcreteCompany(string name)
:base(name)
{

}
public override void Add(Company company)
{
companys.Add(company);
}

public override void Remove(Company company)
{
companys.Remove(company);
}

public override void Display(int depth)
{
Console.WriteLine(new string('-',depth) + name);
foreach(var company in companys)
{
company.Display(depth + 2);
}
}

public override void LineOfDuty()
{
foreach(var company in companys)
{
company.LineOfDuty();
}
}
}

3.Leaf：

public class HRDepartment:Company
{
public HRDepartment(string name)
:base(name)
{

}
public override void Add(Company company)
{

}

public override void Remove(Company company)
{

}

public override void Display(int depth)
{
Console.WriteLine(new string('-', depth) + name);
}

public override void LineOfDuty()
{
Console.WriteLine("{0} 员工招聘培训管理",name);
}
}

public class FinanceDepartment:Company
{
public FinanceDepartment(string name)
: base(name)
{

}
public override void Add(Company company)
{

}

public override void Remove(Company company)
{

}

public override void Display(int depth)
{
Console.WriteLine(new string('-', depth) + name);
}

public override void LineOfDuty()
{
Console.WriteLine("{0} 公司财务收支管理",name);
}
}

4.客户端代码：

class Program
{
static void Main(string[] args)
{
Company rootCompany = new ConcreteCompany("北京总公司");
rootCompany.Add(new HRDepartment("总公司人力资源部"));
rootCompany.Add(new FinanceDepartment("总公司财务部"));

Company eastCompany = new ConcreteCompany("华东分公司");
eastCompany.Add(new HRDepartment("华东分公司人力资源部"));
eastCompany.Add(new FinanceDepartment("华东分公司财务部"));

rootCompany.Add(eastCompany);

Company shanghaiCompany = new ConcreteCompany("上海办事处");
shanghaiCompany.Add(new HRDepartment("上海办事处人力资源部"));
shanghaiCompany.Add(new FinanceDepartment("上海办事处财务部"));

eastCompany.Add(shanghaiCompany);

Console.WriteLine("机构图：");
rootCompany.Display(1);

Console.WriteLine("职责：");
rootCompany.LineOfDuty();
}
}

　　透明方式：Component中声明所有用来管理子对象的方法，其中包括Add、Move等。这样实现Componet接口的所有子类都具备了Add和Remove。这样做的好处就是叶节点和枝节点对于外界没有区别，它们具备完全一致的行为接口。但问题也很明显，因为Leaf类本身不具备Add()、Remove()方法的功能，所以实现它是完全没有意义的。

　　安全方式：Componet中不去声明Add和Remove方法，那么子类Leaf也就不需要去实现它，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，客户端的调用要做相应的判断，带来了不便。