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;}