内存

@interface Teacher : NSObject
-(void)onClass;
@end

#import "Teacher.h"

@implementation Teacher
-(void)onClass
{
    NSLog(@"teacher is on class");
}
@end

#import "Teacher.h"
@interface Student : NSObject
{
    Teacher *_teacher;
}

//@property(nonatomic,retain)Teacher *teacher;
-(void)setTeacher:(Teacher *)aTeacher;
-(Teacher *)teacher;
@end

#import "Student.h"

@implementation Student

//@synthesize teacher = _teacher;
//retain中@synthesize默认手动写法
-(void)setTeacher:(Teacher *)aTeacher
{
    if (_teacher != aTeacher)//不等的时候赋新值
    {
        [_teacher release];//_teacher释放？第一次_teacher是nil(对nil release没影响)，但是如果后面还要把对象赋给_teacher的话，这里必须先释放
        _teacher = [aTeacher retain];//把所有权给_teacher。copy的话这里也改为[aTeacher retain]
        
    }
}
-(Teacher *)teacher
{
    return _teacher;
}



-(Student *)init
{
    self = [super init];
    if (self)
    {
        
    }
    return self;
}

//重写
-(void)dealloc
{
    [_teacher release];//属性中retain，这里也要release
    NSLog(@"我(%@)快要被释放了。。。。。",self);

　　[super dealloc];//第一步必须做的，保留父类释放

} @end

 /*
    Student *s = [[Student alloc]init];
    NSLog(@"reatinCount = %d",s.retainCount);
    
    [s retain];
    NSLog(@"reatinCount = %d",s.retainCount);
    
    [s release];
    NSLog(@"reatinCount = %d",s.retainCount);
    
    [s release];
    NSLog(@"reatinCount = %d",s.retainCount);
    */
    //属性的内存管理
    Teacher *t = [[Teacher alloc]init];
    Teacher *t2 = [[Teacher alloc]init];

    Student *stu = [[Student alloc]init];
    stu.teacher = t;
    stu.teacher = t2;
    
    
    [t release];
    [t2 release];
    
    //sleep(10);//让系统休眠10秒
    
    [stu.teacher onClass];
    [stu release];
/*
    Student *s1 = [[Student alloc]init];
    Student *s2 = s1;
    NSLog(@"s2 = %d",s2.retainCount);
    [s2 retain];//2
    NSLog(@"s1 = %d",s1.retainCount);
    NSLog(@"s2 = %d",s2.retainCount);
    [s1 release];
    NSLog(@"s1 = %d",s1.retainCount);
    NSLog(@"s2 = %d",s2.retainCount);
*/