Review:
给对象发送消息，进行相应的计数器操作。
Retain消息：使计数器+1，改方法返回对象本身
Release消息：使计数器-1（并不代表释放对象）
retainCount消息：获得对象当前的引用计数器值
Management principles:
1 alloc new copy
who create ,who release
2 except (alloc new copy)
Please state autorelease
3 Who retain,who release (anyway)
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@class ---->Key word
// Add content
//When use dealloc
-(void)dealloc{
//self.book=nil;->OK
//[self setBook:nil];->OK
[_book release];
[super dealloc];
}
//Because self.book =setBook . It's a method inside can release book,not visiting //mumber variable.
-(void) setBook:(Book *)book{
if(_book!=book){
[_book realease];
_book=[book retain];
}
}
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@class
In Student.h file
General in development #import "Book.h" will cause some problem in property.
#import "Book.h"
will copy all the things and most of them is useless.
And we want only know Book is a class,I don't want know other things(inheritation&getter&setter)
So in Student.h
Replace #import "Book.h"; as @class Book;