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 0;
}