Objective-C复合

正所谓复合，便是定义的这个类中的成员是另外类的实例方法。

也就是把其他对象作为自身的题部分，以提升自身的功能，

就相当于C语言中的函数嵌套。下面是一段代码(多个文件放在一块了):

 /***Computer类的声明***Computer类的声明***Computer类的声明***/
 #import <Foundation/Foundation.h>

 @interface Computer : NSObject

 @property (nonatomic, strong) NSString *brand;//声明一个字符串对象属性brand

 @end

 /***Computer类的实现***Computer类的实现***Computer类的实现***/
 #import "Computer.h"

 @implementation Computer

 @end

 /***Desk类的声明***Desk类的声明***Desk类的声明***/

 #import <Foundation/Foundation.h>

 @interface Desk : NSObject

 @property (nonatomic, strong) NSString *color;//声明一个字符串对象属性color

 @end

 /***Desk类的实现***Desk类的实现***Desk类的实现***/

 #import "Desk.h"

 @implementation Desk

 @end

 /***ClassRoom类的声明***ClassRoom类的声明***ClassRoom类的声明***/

 #import <Foundation/Foundation.h>
 #import "Desk.h"
 #import "Computer.h"

 @interface ClassRoom : NSObject
 @property (nonatomic, strong) Desk *desk;//声明一个Desk的对象desk的属性 这里用的就是复合
 @property (nonatomic, strong) Computer *computer;////声明一个Computer的对象computer的属性这里用的也是复合
 @end

 /***ClassRoom类的实现***ClassRoom类的实现***ClassRoom类的实现***/

 #import "ClassRoom.h"
 @implementation ClassRoom
 -(NSString *)description{  //库方法，方法的重写
     NSString *str = [NSString stringWithFormat/*方法*/:@"我们的教室有%@的桌子，%@电脑",self/*当前方法的调用者-ClassRoom*/.desk.color,self.computer.brand];
     return str;
 }
 @end

 /***主函数***主函数***主函数***主函数***主函数***主函数***主函数*/

 #import <Foundation/Foundation.h>
 #import "ClassRoom.h"

 int main(int argc, const char * argv[]) {
     @autoreleasepool {

         ClassRoom *classRoom = [[ClassRoom alloc] init];
         Desk *de= [[Desk alloc] init];
         classRoom.desk = de;//给对象的属性（类的对象）赋值，先初始化该属性
         classRoom.desk.color = @"褐色";//给属性的属性赋值

         Computer *com = [[Computer alloc] init];
         com.brand = @"黑苹果";//对象完全初始化之后，再给其所属的对象赋值
         classRoom.computer = com;

        NSLog(@"%@",classRoom);
     }
     return 0;
 }

另一个例子:

 #import <Foundation/Foundation.h>
 //门类
 @interface Door:NSObject
 -(void)open;
 -(void)close;
 @property(nonatomic,strong)NSString *replace;  //实现更换门
 @end
 @implementation Door
 -(void)open
 {
     NSLog(@"开门");
 }
 -(void)close
 {
     NSLog(@"关门");
 }
 -(void)color
 {
     NSLog(@"门得颜色%@",self.replace);
 }
 @end

 //窗户类
 @interface Window:Door
 @end
 @implementation Window
 -(void)open
 {
     NSLog(@"开窗");
 }
 -(void)close
 {
     NSLog(@"关窗");
 }
 @end
 //房屋类
 @interface Housing:NSObject
 //{
 //    Door *door;//门
 //    Window *window;//窗户
 //}
 @property(nonatomic)Door *door;//门
 @property(nonatomic)Window *window;//窗户
 -(void)InAndOut;//进出方法
 -(void)takeAbreath;//换气方法
 @end
 @implementation Housing
 -(void)InAndOut
 {
 //    door = [[Door alloc] init];
     NSLog(@"进屋");
     [_door open];
     NSLog(@"出屋");
     [_door close];
 }//进出方法
 -(void)takeAbreath
 {
  //   window = [[Window alloc] init ];
     [_window open];
     NSLog(@"进气");
     NSLog(@"出气");
     [_window close];
 }//换气方法

 @end
 int main(int argc, const char * argv[])
 {
     @autoreleasepool
     {
         Housing *housing = [[Housing alloc] init];

         housing .door = [[Door alloc] init];
         housing .window =  [[Window alloc] init ];
         [housing InAndOut];
         [housing takeAbreath];
         housing.door.replace = @"红色";
         [housing.door color];
     }
     return ;
 }