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;
 1 // Book类
 2 @interface Book:NSObject
 3 
 4 {
 5 
 6       int _price;  // 书的价格
 7 
 8 }
 9 // Book的 get set方法
10 - (void)setPrice:(int) price;
11 
12 - (int)price;
13 
14 @end
15 
16 @implementation Book
17 - (void)setPrice:(int) price{
18     
19       _price = price;
20 }
21 
22 - (int)price{
23       return _price;
24 }
25 
26 - (void)dealloc{
27    
28     NSLog(@"Book对象被回收");
29     [super dealloc];
30 
31 }
32 @end
33 
34 
35 // Person类的声明与实现  Person.h
36 
37 @interface Person:NSObject
38 {
39        Book *_book;
40 
41 }
42 // get set方法声明
43 - (void)setBook:(Book *) book;
44 - (Book *)book;
45 
46 @end 
47 
48 // Person.m
49 
50 @implementation Person
51 
52 - (void)setBook:(Book *) book{
53 
54       _book = [book retain];  //计数器+1
55 }
56 
57 - (Book *)book{
58       return _book;
59 }
60 
61 // 重写 dealloc
62 - (void)dealloc{
63      [_book release];
64      NSLog(@"person对象被回收");
65      [super dealloc] ;// 最后写super dealloc
66 }
67 @end
68 
69 
70 
71 
72 
73 
74 
75 int main(){
76 
77       Person *p = [ [Person alloc] init ];   // p 计数器 +1
78       Book    *b = [ [Book alloc] init ];     // b 计数器 +1
79      [ p setBook:b];  // 使用Book 时 retain;  b计数器值2
80 
81 
82     [b release];     // 计数器 2 -1 =1
83     
84     [p release];//   p计数器为0调用 Person 的dealloc 对Book release
85     b = nil;
86     p = nil;
87   
88     return 0 ;
89 
90 }