Object-c学习之路二（oc内存管理黄金法则1）

//
//  main.m
//  MemoryManagement
//
//  Created by WildCat on 13-7-23.
//  Copyright (c) 2013年 wildcat. All rights reserved.
//

#import <Foundation/Foundation.h>
#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;
}

//  Student.h
//  MemoryManagement
//
//  Created by WildCat on 13-7-23.
//  Copyright (c) 2013年 wildcat. All rights reserved.
//

#import <Foundation/Foundation.h>
#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

//  Book.h
//  MemoryManagement
//
//  Created by WildCat on 13-7-23.
//  Copyright (c) 2013年 wildcat. All rights reserved.
//

#import <Foundation/Foundation.h>

@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