黑马程序员_set方法内存管理



黑马程序员_set方法内存管理

内存管理代码规范：
1.只要调用alloc，必须有release(autorelease)
  如果对象不是通过alloc产生的，就不需要release

2.set方法代码规范:
  * 基本数据类型：直接赋值
    - (void)setAge:(int)age
    {
     _age = age;
    }

  * OC对象类型
- (void)setCar:(Car *)car
{
 // 1.先判断是不是新传进来的对象
 if ( car != _car )
 {
  // 2.对旧对象做一次release
  [_car release];
 
  // 3.对新对象组一次retain; 并赋值给_car
  _car = [car retain];
 }
}

3.dealloc方法的代码规范
  * 一定要调用[super dealloc]; 一定要放到最后面。
 
  * 对当前对象(self)所拥有的其他对象做一次release
- (void)dealloc
{
 [_car release];

 [super dealloc];
}

#import <Foundation/Foundation.h>/****************** Person ******************/@interface Person : NSObject{Car *_car;int _age;}- (void)setAge:(int)age;- (int)age;- (void)setCar:(Car *)car;- (Car *)car;@end@implementation Person- (void)setAge:(int)age{// 基本数据类型是不需要管理内存的_age = age;}- (int)age{return _age;}- (void)setCar:(Car *)car{// 对当前正在使用的车（旧车）做一次releaseif ( car != _car ){[_car release];// 第一次赋值时 [nil release]什么也不做// 对新车做一次retain操作_car = [car retain];}}- (Car *)car{return _car;}- (void)dealloc{// 当Person对象回收了，代表不用Car对象了// 对Car对象做一次release操作[_car release];NSLog (@"Person --- -dealloc: age = %d", _age);[super dealloc];}@end/****************** Car ******************/@interface Car : NSObject{int _speed;}- (void)setSpeed:(int)speed;- (int)speed;@end@implementation Car- (void)setSpeed:(int)speed{_speed = speed;}- (int)speed{return _speed;}- (void)dealloc{/*  * _speed: 直接访问成员变量 * self->speed: 直接访问成员变量 * self.speed: 通过get方法访问成员变量 * [self speed]: 通过get方法访问成员变量 */NSLog (@"Car --- -dealloc: speed = %d", _speed);// _speed == self.speed == self->_speed;[super dealloc];}@end/****************** Dog ******************/@interface Dog : NSObject@end@implementation Dog@end/****************** Student ******************/@interface Student : NSObject{int _no;NSString *_name;car *_car;Dog *_dog;}- (void)setNo:(int)no;- (int)no;- (void)setName:(NSString *)name;- (NSStirng *)name;- (void)setCar:(Car *)car;- (Car *)car;- (void)setDog:(Dog *)dog;- (Dog *)dog;@end@implementation Student- (void)setNo:(int)no{_no = no;}- (int)no{return _no;}- (void)setName:(NSString *)name{if ( name != _name ){[_name release];_name = [name retain];}}- (NSStirng *)name{return _name;}- (void)setCar:(Car *)car{if ( car != _car ){[_car release];_car = [car retain];}}- (Car *)car{return _car;}- (void)setDog:(Dog *)dog{if ( dog = _dog ){[_dog release];_dog = [dog retain];}}- (Dog *)dog{return _dog;}- (void)dealloc{[_name release];[_dog release];[_car release];[super dealloc];}@end/****************** main ******************/int main(){// stu-1Student *stu = [[Student alloc] init];// car-2// 这行代码有内存泄漏// stu.car = [[Car alloc] init];// stu-0; car-1[stu release];// 这行代码有内存泄漏// [Car alloc] init].speed = 100;return 0;}void test3(){Student *stu = [[Student alloc] init];Car *c = [[Car alloc] init];stu.car = c;Dog *d = [[Dog alloc] init];stu.dog = d;stu.name = @"jack";[d release];[c release];[stu release];}void test2(){Person *p1 = [[Person alloc] init];p.age = 20;Car *c1 = [[Car alloc] init];c1.speed = 100;p1.car = c1;Car *c2 = [[Car alloc] init];c2.speed = 200;[c2 release];[c1 release];[p1 release];}void test1(){// p-1Person *p = [[Person alloc] init];p.age = 20;// c1-1Car *c1 = [[Car alloc] init];c1.speed = 250;// c1-2p.car = c1;// c1-1[c1 release];// c1-0 僵尸对象// p.car = c1;[p release];}void test(){// p-1Person *p = [[Person alloc] init];p.age = 20;// c1-1Car *c1 = [[Car alloc] init];c1.speed = 250;// p想拥有c1// c1-2p.car = c1;// [p setCar:c1];// c2-1Car *c2 = [[Car alloc] init];c2.speed = 300;// p将车换成了c2// c2-2; c1-1;p.car = c2;// c2-1[c2 release];// c1-1[c1 release];// p-0; c2-0; c1-0;[p release];}