创建class Book
.h 有@ property float price; //@synthesize 自动
------------
创建class Student
#import "Book.h"
.h 有@property int age;
@property Book *book; //@synthesize 自动
--------------
验证Student对象是否回收
Student.m
-(void)dealloc{
NSLog(@"Student :%i 被销毁了"，_age);
[super dealloc];
}
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为了方便访问_age 创建可以传入_age 的构造方法
Student.h
-(id)initWithAge:(int)age;
student.m
-(id)initWithAge:(int)age{
if(self=[super init]){ //如果super返回的对象不为空
_age=age;
}
return self;
}
----------------------
验证Book对象是否回收
Book.m
-(void)dealloc{
NSLog(@" book:%f 被销毁了"，_price);
[super dealloc];
}
----------------------------
//with _price Book constructor
Book.h
-(void)initWithPrice:(float)price;
Book.m
-(void)initWithPrice:(float)price{
if(self=[super init]){ //如果super返回的对象不为空
_price=price;
}
}
----------------------------
annotation method
1 #pragma mark constructor
(advantage:easy:locate)
2 #pragma mark -groupname
(advantage :group)
3 Of course // can work
----------------------------
main.m
#import "Book.h"
#import "Student.h"
main(){
@autoreleasepool{
Student *stu=[[Student alloc]initWithAge:10]; //stu 1
Book *book =[[Book alloc]initWithPrice:3.5];// book 1
stu.book=book;// In reality never use this way//book 1
[book release];//book 0
[stu release];//stu 0
}
return 0;
}
---------------------------------
Student.m
//manually realize getter & setter
//Standard realization of getter and setter
Student.h // Because u do manually so XCode will not call @synthesize, so there is no //_book,so we need to state _book ourself.
@interface Student:NSObject{
Book *_book;
}
Student.m
-(void)setBook:(Book *)book{
_book=book;
}
-(Book *)book{
return _book;
}
// Abopve six line can be short for
//@synthesize book=_book;
---------------------------------------
Then counter
-----------------------------------------
// When we developing in reality ,we may use object
//so change code
//main.m
void test (Student *stu){
Book *book=[[Book alloc]initWithPrice:3.5];
stu.book=book;
[book release];
}
void test1(Student *stu){
//add reading method
//Student.h -(void)readBook;
//Student.m
//-(void)readBook{
//NSLog(@"Reading book is:%f",_book.price);
//}
[stu readBook];// not safe ,visiting _book,because in test book is released so (wild pointer)
}
-------------------------
//change code
main(){
test(stu);
test1(stu);
}
-----------------------------
//student want to make use of book object so, retain book in Student
//setBook retain;stu alloc release
---------------------------------
//Improve code
// so compare the passed book object with current book object if not the same one,
//release the previous one.
-(void)setBook:(Book *)book{
if(self.book!=book){
[_book release]; // empty pointer is safe.
_book=[book retain];
}
}
//被释放（-1）和被销毁（0）不同