Object-C学习笔记四-----组合_object-c 组合-优快云博客

本文链接：https://blog.youkuaiyun.com/lutaotony/article/details/6769003

本文通过一个汽车组成的实例，详细讲解了组合模式（Composition）在Objective-C中的应用。文章演示了如何创建基本组件（如轮胎和发动机），并通过这些组件构建更复杂的对象（如汽车）。此外，还介绍了如何使用继承来扩展基本组件的功能。

前面学习的时候知道继承是两个类之间的关系。

一个项目可能会有很多部分组成。我们如何能更好的把他们组合在一起呢？我们认为在对象之间的才称之为composition.

就像一辆汽车由发动机和四个轮子组成。这样我们可以理解为一个汽车类由一个发动机类和轮子类组成。只有有了发动机和轮子才能有车子。所以我们要先创建轮子和发动机。

@interface Tire : NSObject
@end

@implementation Tire

-(NSString *) description
{
return (@"I am a tire.I last a while.");
}
@end

@interface Engine : NSObject
@end

@implementation Engine

-(NSString *) description
{
return (@"I am a engine, Vrooom!");
}
@end

@interface Car : NSObject {
@private
Engine *engine;
Tire *tires[4];
}

-(void) setEngine:(Engine *) newEngine;
-(Engine *) Engine;

-(void) setTire:(Tire *) tire atindex:(int)index;
-(Tire *) tireatIndex :(int) index;

-(void) print;
@end//Car

@implementation Car

-(id) init
{
    if(self=[super init])
    {
        engine= [Engine new];
        tires[0]=[Tire new];
        tires[1]=[Tire new];
        tires[2]=[Tire new];
        tires[3]=[Tire new];
    }
    return self;
}

-(void) setEngine:(Engine *)newEngine
{
engine = newEngine;
}

-(Engine *)Engine
{
return engine;
}

-(void) setTire:(Tire *)tire atindex:(int)index
{
    if(index<0||index>3)
    {
        NSLog(@"bad index %d in setTire:atindex:",index);
        exit(1);
    }
    tires[index]=tire;
}

-(Tire *)tireatIndex:(int)index
{
    if(index<0||index>3)
    {
        NSLog(@"bad index %d in setTire:atindex:",index);
        exit(1);
    }
    return tires[index];
}

-(void) print
{
    NSLog(@"%@",engine);
    NSLog(@"%@", tires[0]);
     NSLog(@"%@", tires[1]);
     NSLog(@"%@", tires[2]);
     NSLog(@"%@", tires[3]);
}
@end

然后我们在main函数中实例化车类。

实例化车类 Car *car =[Car new]；而c# 实例化是 Car car = new Car；

调用车类中的方法[car print]；调用方法是 car.print();

轮子和发动机都有很多种，但是他们都是轮子和发动机，所以具体的轮子和发动机继承他们相应的类。

@interface AllWeatherRadial : Tire
@end

@implementation AllWeatherRadial

-(NSString *) description
{
return (@"I am a tire for rain or shine");
}
@end

@interface AllWeatherRadial : Tire
@end

@implementation AllWeatherRadial

-(NSString *) description
{
return (@"I am a tire for rain or shine");
}
@end

int main (int argc, const char * argv[])
{
    Car *car=[Car new];
    //Engine *engine =[Engine new];
     Engine *engine =[Slant6 new];
    [car setEngine:engine];


    for (int i=0 ; i<4; i++) {
        //Tire *tire=[Tire new];
        Tire *tire=[AllWeatherRadial new];
        [car setTire:tire atindex:i];

    }
    [car print];
    return 0;
}