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1. 内存管理补充：

1.1. setter方法：

@autoreleasepool {#pragma 验证Person类dealloc方法里的：[_car release]        {        Person *p = [[Person alloc] init];        Car *c = [[Car alloc] init];        [c setSpeed:100];        [p setCar:c];                [p go];        [c release];                [p go];        [p go];        [p release];        }#pragma 验证Person类setCar方法里的：[_car release]        {            Person *p = [[Person alloc] init];            Car *bmw = [[Car alloc] init];            [bmw setSpeed:100];            [p setCar:bmw];            [p go];            [bmw release];                        Car *byd = [Car new];            [byd setSpeed:80];            [p setCar:byd];            [p go];            [byd release];            [p release];                                }#pragma 验证Person类setCar方法里的：if (_car != car)        {        Person *liubo = [Person new];        Car *bicycle = [Car new];// 1        bicycle.speed = 80;        [liubo setCar:bicycle];// 2                [bicycle release];// 1        [liubo setCar:bicycle];  // 访问僵尸对象肯定会崩，你又不能起死回生。。所以要写if那句话        [liubo go];        [liubo release];        }        // 类用assign可能会造成野指针和内存泄露的问题 所以要使用retain    }

#import 
   
    @class Car;@interface Person : NSObject{    Car *_car;}//@property (nonatomic,retain) Car *car;- (void)setCar:(Car *)car;- (void)go;@end#import "Person.h"#import "Car.h"@implementation Person- (void)setCar:(Car *)car{    if (_car != car) {        [_car release];        _car = [car retain];    }    }- (void)go{        [_car run];}- (void)dealloc{    [_car release];    NSLog(@"people is over");    [super dealloc];}@end
   

#import 
   
    @interface Car : NSObject{    int _speed;}- (void)setSpeed:(int)speed;- (void)run;@end#import "Car.h"@implementation Car- (void)setSpeed:(int)speed{    _speed = speed;}- (void)run{    NSLog(@"The car is running  速度：%d.", _speed);}- (void)dealloc{    NSLog(@"%d car is over",_speed);    [super dealloc];}@end
   

1.2. 多态：

Animal *d = [Dog new];        // 多态：没有继承就不能实现多态机制，父类指针可以指向不同的子类对象

1.3. collection：

Person *p = [[Person alloc] init];        // 如果数组创建是用[[NSMutableArray alloc] init]，则需要在用完后：对数组进行release    NSMutableArray *array = [NSMutableArray array];        //  把对象放到数组中的时候，对象的引用计数会+1    [array addObject:p];    NSLog(@"%lu", p.retainCount); // 结果是：2        // 从数组中移除的时候，引用计数-1    [array removeObject:p];    NSLog(@"%lu", p.retainCount); // 结果是：1        [p release];

添加对象时，会对这个对象retain一次

移除对象时，会对这个对象release一次

对象销毁时，集合会对集合中包含的所有对象发送一条release消息

add/insert ：计数器+1

remove/delete ：计数器-1

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