OC MRC之多对象之间管理（代码分析）

#import <Foundation/Foundation.h>

@interface Book : NSObject
{
    int _price;
}

- (void)setPrice:(int)price;
- (int)price;

@end

#import "Book.h"

@implementation Book

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

- (int)price
{
    return _price;
}
- (void)dealloc
{
    NSLog(@"Book对象被回收");
    [super dealloc];
}
@end








#import <Foundation/Foundation.h>
#import "Book.h"

@interface Person : NSObject
{
    Book *_book;
}

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

@end

#import "Person.h"

@implementation Person
- (void)setBook:(Book *)book
{
    _book = [book retain];
}

- (Book *)book
{
    return _book;
}

- (void)dealloc
{
    [_book release];
    NSLog(@"Person对象被回收");
    [super dealloc];
}
@end







/*
 1.你想使用（占用）某个对象，就应该让对象的计数器+1（让对象做一次retain操作）
 2.你不想再使用（占用）某个对象，就应该让对象的计数器-1（让对象做一次release）
 
 3.谁retain，谁release
 
 4.谁alloc，谁release
 */

#import <Foundation/Foundation.h>
#import "Person.h"
#import "Book.h"

int main()
{
    // b-1
    Book *b = [[Book alloc] init];
    // p-1
    Person *p1 = [[Person alloc] init];
    
    //p1想占用b这本书
    // b-2
    [p1 setBook:b];
    
    // p-0
    // b-1
    [p1 release];
    p1 = nil;
    
    // b-0
    [b release];
    b = nil;
    return 0;
}