组合模式(Component Pattern)

1 代码

每一个公司都有自己的组织结构，越是大型的企业，其组织结构就会越复杂。大多数情况下，公司喜欢用“树形”结构来组织复杂的公司人事关系和公司间的结构关系。一般情况下，根结点代表公司的最高行政权利单位，分支节点表示一个个部门，而叶子结点则会用来代表每一个员工。每一个结点的子树，表示该结点代表的部门所管理的单位。假设一个具有HR部门，财务部门和研发部门，同时在全国有分支公司的总公司，其公司结构，可以表示成如下逻辑：



In [1]:

    
class Company:
    name = ''
    def __init__(self, name):
        self.name = name
    def add(self, company):
        pass
    def remove(self, company):
        pass
    def display(self, depth):
        pass
    def listDuty(self):
        pass

class ConcreteCompany(Company):
    childrenCompany = None
    def __init__(self, name):
        Company.__init__(self,name)
        self.childrenCompany = []
    def add(self, company):
        self.childrenCompany.append(company)
    def remove(self, company):
        self.childrenCompany.remove(company)
    def display(self, depth):
        print('-'*depth + self.name)
        for component in self.childrenCompany:
            component.display(depth+1)
    def listDuty(self):
        for component in self.childrenCompany:
            component.listDuty()



In [2]:

    
class HRDepartment(Company):
    def __init__(self, name):
         Company.__init__(self,name)
    def display(self, depth):
        print ('-'*depth + self.name)
    def listDuty(self): #履行职责
        print ('%s\t Enrolling & Transfering management.' % self.name)
class FinanceDepartment(Company):
    def __init__(self, name):
        Company.__init__(self,name)
    def display(self, depth):
        print ("-" * depth + self.name)
    def listDuty(self): #履行职责
        print ('%s\tFinance Management.'%self.name)

class RdDepartment(Company):
    def __init__(self,name):
        Company.__init__(self,name)
    def display(self, depth):
        print ("-"*depth+self.name)
    def listDuty(self):
        print ("%s\tResearch & Development."% self.name)

在该例中，公司结构抽象仅考虑公司（ConcreteCompany）和部门（Department），公司有子公司的可能性，公司也有自己的部门，部门是最终的叶子结点。假设总公司下设东边的分公司一个，东边的分公司下设东北公司和东南公司，显示公司层级，并罗列这些的公司中各部门的职责，可以构建如下业务场景：



In [3]:

    
root = ConcreteCompany('HeadQuarter')
root.add(HRDepartment('HQ HR'))
root.add(FinanceDepartment('HQ Finance'))
root.add(RdDepartment("HQ R&D"))

comp = ConcreteCompany('East Branch')
comp.add(HRDepartment('East.Br HR'))
comp.add(FinanceDepartment('East.Br Finance'))
comp.add(RdDepartment("East.Br R&D"))
root.add(comp)

comp1 = ConcreteCompany('Northast Branch')
comp1.add(HRDepartment('Northeast.Br HR'))
comp1.add(FinanceDepartment('Northeast.Br Finance'))
comp1.add(RdDepartment("Northeast.Br R&D"))
comp.add(comp1)

comp2 = ConcreteCompany('Southeast Branch')
comp2.add(HRDepartment('Southeast.Br HR'))
comp2.add(FinanceDepartment('Southeast.Br Finance'))
comp2.add(RdDepartment("Southeast.Br R&D"))
comp.add(comp2)

root.display(1)

root.listDuty()









    



-HeadQuarter
--HQ HR
--HQ Finance
--HQ R&D
--East Branch
---East.Br HR
---East.Br Finance
---East.Br R&D
---Northast Branch
----Northeast.Br HR
----Northeast.Br Finance
----Northeast.Br R&D
---Southeast Branch
----Southeast.Br HR
----Southeast.Br Finance
----Southeast.Br R&D
HQ HR	 Enrolling & Transfering management.
HQ Finance	Finance Management.
HQ R&D	Research & Development.
East.Br HR	 Enrolling & Transfering management.
East.Br Finance	Finance Management.
East.Br R&D	Research & Development.
Northeast.Br HR	 Enrolling & Transfering management.
Northeast.Br Finance	Finance Management.
Northeast.Br R&D	Research & Development.
Southeast.Br HR	 Enrolling & Transfering management.
Southeast.Br Finance	Finance Management.
Southeast.Br R&D	Research & Development.

2 Discription

组合模式也叫作部分-整体模式，其定义如下：将对象组合成树形结构以表示“部分”和“整体”的层次结构，使得用户对单个对象和组合对象的使用具有一致性。

3 Advantages

节点增加和减少是非常自由和方便的，这也是树形结构的一大特点；
所有节点，不管是分支节点还是叶子结点，不管是调用一个结点，还是调用一个结点群，都是非常方便的。

4 Usages

维护部分与整体的逻辑关系，或者动态调用整体或部分的功能接口

5 Disadvantages

由于叶子结点和分支结点直接使用了实现类，而不方便使用抽象类，这大大限制了接口的影响范围；若结点接口发生变更，对系统造成的风险会比较大