OC面向对象的三大特征(封装 继承 多态)习题2 复合

复合:一个类中有一个成员变量是另外一个类的对象。

比如我现在要制作一台电脑，电脑需要CPU，显示器，鼠标和键盘等。这些东西的研发都是很复杂的过程。如果现在有成型的CPU等组件，就可以直接用这些组件攒一台电脑。复合模式就是这样。

习题2

汽车安装发动机和4个轮胎。

(1)定义三个类：汽车类。

(2)定义发动机类，实例变量（品牌、价格）

(3)定义轮胎类，实例变量（品牌、价格、安装位置）。方法：添加防滑链。

(4)给汽车类添加一个实例变量发动机，添加一个数组(使用Tire * tires[4])管理汽车的4个轮胎。

(5)汽车安装发动机和4个轮胎。

工程解析(@public 懒得写set get方法,主要看复合过程)

Engine.h

#import <Foundation/Foundation.h>

@interface Engine : NSObject
{
@public
NSString *_Brand;
int _Price;
}
-(void)Run;
@end

Engine.m

#import "Engine.h"

@implementation Engine
-(void)Run
{
NSLog(@"发动机(品牌%@,价格%d)启动了",_Brand,_Price);
}
@end

Tire.h

#import <Foundation/Foundation.h>

@interface Tire : NSObject
{
@public
NSString *_Brand;
int _Price;
int _Location;
}
-(void)install;
-(void)Run;
@end

Tire.m

#import "Tire.h"

@implementation Tire
-(void)install
{
NSLog(@"在%d上安装防滑链",_Location);
}
-(void)Run
{
NSLog(@"位置%d,品牌%@,价格%d的轮胎转动",_Location,_Brand,_Price);
}
@end

Car.h

#import <Foundation/Foundation.h>
#import "Engine.h"
#import "Tire.h"
@interface Car : NSObject
{
@public
NSString *_Brand;
int _Price;
Engine *_engine;
Tire *tires[4];
}
-(void)setEngine:(Engine *)Engine;
-(Engine *)Engine;
//因为是一个数组,set get 写法有变化
-(void)setTire:(Tire *)tire atIndex:(int)index;
-(Tire *)tireAtIndex:(int)index;
-(void)start;//汽车启动
@end

Car.m

#import "Car.h"

@implementation Car

-(void)setEngine:(Engine *)Engine
{
_engine=Engine;
}
-(Engine *)Engine
{
return _engine;
}
-(void)setTire:(Tire *)tire atIndex:(int)index
{
tires[index]=tire;
}
-(Tire *)tireAtIndex:(int)index
{
return tires[index];
}
-(void)start
{
NSLog(@"汽车(品牌%@,价格%d)启动",_Brand,_Price);
[_engine Run];
for (int i=0; i<4; i++) {
[tires[i] Run];
[tires[i] install];
}

}
@end

main.m

#import <Foundation/Foundation.h>
#import "Car.h"
#import "Engine.h"
#import "Tire.h"
int main(int argc, const char * argv[]) {
@autoreleasepool {
Car *p=[[Car alloc]init];
p->_Brand=@"Audi";
p->_Price=600000;

Engine *p1=[[Engine alloc]init];
p1->_Brand=@"丰田4Y";
p1->_Price=2000;

Tire *tires[4];
for (int i=0; i<4; i++) {
tires[i]=[[Tire alloc]init];
tires[i]->_Brand=@"固特异";
tires[i]->_Price=500;
tires[i]->_Location=i+1;
[p setTire:tires[i] atIndex:i];
}
[p setEngine:p1];
[p start];
}
return 0;
}