今天看了看oc的内存管理，自己管理内存不能随便的release和retain 法则会出现野指针等错误。下面以人和读书的例子做练习。

1.主函数

 

////  main.m//  MemoryManagement////  Created by WildCat on 13-7-23.//  Copyright (c) 2013年 wildcat. All rights reserved.//#import 
    
     #import "Student.h"#import "Book.h"void test1(){        Student *stu=[[Student alloc] init];        [stu retain];        NSLog(@"stu 的计算器为：%zi",[stu retainCount]);//2    [stu release];//1    [stu release];//0    }#pragma mark 添加书void addBook(Student *stu){    Book *book=[[Book alloc] initWithPrice:3.5];    stu.book=book;    [book release];        Book *book2=[[Book alloc] initWithPrice:4.5];    stu.book=book2;    [book2 release];}#pragma mark 读书void readBooks(Student *stu){    [stu readBook];}#pragma mark 主函数int main(int argc, const char * argv[]){    @autoreleasepool {        Student *stu=[[Student alloc] initWithAge:22];        Student *stu1=[[Student alloc] initWithAge:20];        addBook(stu1);        readBooks(stu1);                addBook(stu);        readBooks(stu);        [stu release];//多写[stu release]会出现野指针错误，[nil release]则不会        [stu1 release];                  }    return 0;}
    

 

2.Student函数

 

//  Student.h//  MemoryManagement////  Created by WildCat on 13-7-23.//  Copyright (c) 2013年 wildcat. All rights reserved.//#import 
    
     #import "Book.h"@interface Student : NSObject{    int _age;    Book *_book;}@property int age;@property Book *book;-(id)initWithAge:(int)age;-(void) readBook;@end
    

 

////  Student.m//  MemoryManagement////  Created by WildCat on 13-7-23.//  Copyright (c) 2013年 wildcat. All rights reserved.//#import "Student.h"@implementation Student@synthesize age=_age;-(Book *)getBook{    return _book;}-(void)setBook:(Book *)book{    if (_book!=book){        //先释放旧的        [_book release];        //再retain 新的        _book=[book retain];    }       }//重写dealloc方法，当对象的计数器是1时自动调用该方法#pragma mark - 静态方法#pragma mark 回收对象- (void)dealloc{    [_book release];    NSLog(@"Student %i,内存被释放。",_age);    [super dealloc];}#pragma mark - 公共方法#pragma mark 读书-(void)readBook{    NSLog(@"当前读的书为：%f",_book.price);}#pragma mark 构造函数-(id)initWithAge:(int)age{    if(self=[super init]){        _age=age;    }        return self;}@end

 

3.Book函数

 

//  Book.h//  MemoryManagement////  Created by WildCat on 13-7-23.//  Copyright (c) 2013年 wildcat. All rights reserved.//#import 
    
     @interface Book : NSObject{    float _price;}@property float price;-(id) initWithPrice:(float)price;@end
    

 

//  Book.m//  MemoryManagement////  Created by WildCat on 13-7-23.//  Copyright (c) 2013年 wildcat. All rights reserved.//#import "Book.h"@implementation Book@synthesize price=_price;#pragma mark 注销函数-(void)dealloc{    NSLog(@"Book %f ,被销毁。",_price);    [super dealloc];}#pragma mark 构造函数-(id) initWithPrice:(float)price{      if (self=[super init]){       _price=price;    }    return self;}@end