移动开发之设计模式-组合模式(IOS&Android)

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组合模式

组合模式（Composite Pattern），又叫部分整体模式，是用于把一组相似的对象当作一个单一的对象。组合模式依据树形结构来组合对象，用来表示部分以及整体层次。这种类型的设计模式属于结构型模式，它创建了对象组的树形结构。
这种模式创建了一个包含自己对象组的类。该类提供了修改相同对象组的方式。
我们通过下面的实例来演示组合模式的用法。实例演示了一个组织中员工的层次结构。

介绍

意图： 将对象组合成树形结构以表示"部分-整体"的层次结构。组合模式使得用户对单个对象和组合对象的使用具有一致性。
主要解决：它在我们树型结构的问题中，模糊了简单元素和复杂元素的概念，客户程序可以向处理简单元素一样来处理复杂元素，从而使得客户程序与复杂元素的内部结构解耦。
何时使用： 1、您想表示对象的部分-整体层次结构（树形结构）。 2、您希望用户忽略组合对象与单个对象的不同，用户将统一地使用组合结构中的所有对象。
如何解决： 树枝和叶子实现统一接口，树枝内部组合该接口。
关键代码： 树枝内部组合该接口，并且含有内部属性 List，里面放 Component。
应用实例： 1、算术表达式包括操作数、操作符和另一个操作数，其中，另一个操作符也可以是操作数、操作符和另一个操作数。 2、在 JAVA AWT 和 SWING 中，对于 Button 和 Checkbox 是树叶，Container 是树枝。
优点： 1、高层模块调用简单。 2、节点自由增加。
缺点： 在使用组合模式时，其叶子和树枝的声明都是实现类，而不是接口，违反了依赖倒置原则。
使用场景： 部分、整体场景，如树形菜单，文件、文件夹的管理。
注意事项： 定义时为具体类。

Android上的组合模式

View&ViewGroup

IOS上的组合模式

UIView的直观结构

UIView的层次结构

很直观的例子

Android

Employee.java

import java.util.ArrayList;
import java.util.List;
 
public class Employee {
   private String name;
   private String dept;
   private int salary;
   private List<Employee> subordinates;
 
   //构造函数
   public Employee(String name,String dept, int sal) {
      this.name = name;
      this.dept = dept;
      this.salary = sal;
      subordinates = new ArrayList<Employee>();
   }
 
   public void add(Employee e) {
      subordinates.add(e);
   }
 
   public void remove(Employee e) {
      subordinates.remove(e);
   }
 
   public List<Employee> getSubordinates(){
     return subordinates;
   }
 
   public String toString(){
      return ("Employee :[ Name : "+ name 
      +", dept : "+ dept + ", salary :"
      + salary+" ]");
   }   
}

DEMO

public class CompositePatternDemo {
   public static void main(String[] args) {
      Employee CEO = new Employee("John","CEO", 30000);
 
      Employee headSales = new Employee("Robert","Head Sales", 20000);
 
      Employee headMarketing = new Employee("Michel","Head Marketing", 20000);
 
      Employee clerk1 = new Employee("Laura","Marketing", 10000);
      Employee clerk2 = new Employee("Bob","Marketing", 10000);
 
      Employee salesExecutive1 = new Employee("Richard","Sales", 10000);
      Employee salesExecutive2 = new Employee("Rob","Sales", 10000);
 
      CEO.add(headSales);
      CEO.add(headMarketing);
 
      headSales.add(salesExecutive1);
      headSales.add(salesExecutive2);
 
      headMarketing.add(clerk1);
      headMarketing.add(clerk2);
 
      //打印该组织的所有员工
      System.out.println(CEO); 
      for (Employee headEmployee : CEO.getSubordinates()) {
         System.out.println(headEmployee);
         for (Employee employee : headEmployee.getSubordinates()) {
            System.out.println(employee);
         }
      }        
   }
}

结果

Employee :[ Name : John, dept : CEO, salary :30000 ]
Employee :[ Name : Robert, dept : Head Sales, salary :20000 ]
Employee :[ Name : Richard, dept : Sales, salary :10000 ]
Employee :[ Name : Rob, dept : Sales, salary :10000 ]
Employee :[ Name : Michel, dept : Head Marketing, salary :20000 ]
Employee :[ Name : Laura, dept : Marketing, salary :10000 ]
Employee :[ Name : Bob, dept : Marketing, salary :10000 ]

IOS

Employee.h

#import <Foundation/Foundation.h>

@interface Employee : NSObject
@property (nonatomic, strong) NSString *name;
@property (nonatomic, strong) NSString *dept;
@property (nonatomic, assign) NSInteger salary;
@property (nonatomic, strong) NSMutableArray *subordinates;

-(instancetype)initWithName:(NSString*)name dept:(NSString*)dept salary:(NSInteger)salary;
-(void)add:(Employee*)e;
-(void)remove:(Employee*)e;
-(NSMutableArray*)getSubordinates;
-(void)callAll:(void(^)(Employee*))call;
@end

Employee.m

#import "Employee.h"

@implementation Employee
{
    //全设置成私有的, 为了演示
    @private
    NSString *name_;
    NSString *dept_;
    NSInteger salary_;
    NSMutableArray *subordinates_;
}
@synthesize name=name_, dept=dept_, salary=salary_, subordinates=subordinates_;

- (instancetype)initWithName:(NSString *)name dept:(NSString *)dept salary:(NSInteger)salary{
    if(self = [self init]) {
        self.name = name;
        self.dept = dept;
        self.salary = salary;
        subordinates_ = [[NSMutableArray alloc]init];
    }
    return self;
}

- (void)add:(Employee *)e{
    [subordinates_ addObject:e];
}
- (void)remove:(Employee *)e{
    [subordinates_ removeObject:e];
}
- (NSMutableArray *)getSubordinates{
    return subordinates_;
}

- (NSString *)description
{
    return [NSString stringWithFormat:@"Employee : [Name : %@, dept : %@,  salary : %ld", name_, dept_, salary_];
}

-(void)callAll:(void(^)(Employee*))callEmployee{
    for (Employee * emp in subordinates_) {
        callEmployee(emp);
        if([[emp getSubordinates] count]>0) {
            [emp callAll:callEmployee];
        }
    }
}
@end

ViewController.h

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    
    Employee *CEO = [[Employee alloc]initWithName:@"John" dept:@"CEO" salary:30000];
    
    Employee *headSales = [[Employee alloc]initWithName:@"Robert" dept:@"Head Sales" salary:20000];
    
    Employee *headMarketing = [[Employee alloc]initWithName:@"Michel" dept:@"Head Marketing" salary:20000];
    
    Employee *clerk1 = [[Employee alloc]initWithName:@"Laura" dept:@"Marking" salary:10000];
    Employee *clerk2 = [[Employee alloc]initWithName:@"Bob" dept:@"Marking" salary:10000];
    
    
    Employee *salesExecutive1 = [[Employee alloc]initWithName:@"Richard" dept:@"Sales" salary:10000];
    Employee *salesExecutive2 = [[Employee alloc]initWithName:@"Rob" dept:@"Sales" salary:10000];
    
    
    [CEO add:headSales];
    [CEO add:headMarketing];
    
    [headSales add:salesExecutive1];
    [headSales add:salesExecutive2];
    
    [headMarketing add:clerk1];
    [headMarketing add:clerk2];
    
    //打印该组织的所有员工
    NSLog(@"%@", [CEO description]);
    [CEO callAll:^(Employee *employee) {
        NSLog(@"%@", [employee description]);
    }];
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

@end

结果

Employee : [Name : John, dept : CEO,  salary : 30000
Employee : [Name : Robert, dept : Head Sales,  salary : 20000
Employee : [Name : Richard, dept : Sales,  salary : 10000
Employee : [Name : Rob, dept : Sales,  salary : 10000
Employee : [Name : Michel, dept : Head Marketing,  salary : 20000
Employee : [Name : Laura, dept : Marking,  salary : 10000
Employee : [Name : Bob, dept : Marking,  salary : 10000