OC内存管理示例

1. 谁 alloc ,谁 release;

2. 谁要占用谁retain;

3. 谁不想占用对象时就 让对象计数器release;

4.谁 retain,谁release;

// Book类
@interface Book:NSObject

{

      int _price;  // 书的价格

}
// Book的 get set方法
- (void)setPrice:(int) price;

- (int)price;

@end

@implementation Book
- (void)setPrice:(int) price{
    
      _price = price;
}

- (int)price{
      return _price;
}

- (void)dealloc{
   
    NSLog(@"Book对象被回收");
    [super dealloc];

}
@end


// Person类的声明与实现  Person.h

@interface Person:NSObject
{
       Book *_book;

}
// get set方法声明
- (void)setBook:(Book *) book;
- (Book *)book;

@end 

// Person.m

@implementation Person

- (void)setBook:(Book *) book{

      _book = [book retain];  //计数器+1
}

- (Book *)book{
      return _book;
}

// 重写 dealloc
- (void)dealloc{
     [_book release];
     NSLog(@"person对象被回收");
     [super dealloc] ;// 最后写super dealloc
}
@end







int main(){

      Person *p = [ [Person alloc] init ];   // p 计数器 +1
      Book    *b = [ [Book alloc] init ];     // b 计数器 +1
     [ p setBook:b];  // 使用Book 时 retain;  b计数器值2


    [b release];     // 计数器 2 -1 =1
    
    [p release];//   p计数器为0调用 Person 的dealloc 对Book release
    b = nil;
    p = nil;
  
    return 0 ;

}