iOSARC下循环引用的问题-举例说明strong和weak的区别

strong:适用于OC对象，作用和非ARC中的retain作用相同，它修饰的成员变量为强指针类型
weak:适用于OC对象，作用和非ARC中的assign作用相同，修饰的成员变量为弱指针类型
assign:适用于非OC对象类型

在OC对象循环引用的时候一端为strong类型，另一段为weak类型

示例代码如下：

/****************************** Teacher.h文件 ***********************************/#import <Foundation/Foundation.h>@class Student;@interface Teacher : NSObject@PRoperty (nonatomic,strong) Student *student;@property (nonatomic,strong) NSString *teacherName;@end/****************************** Teacher.m文件 ***********************************/#import "Teacher.h"#import "Student.h"@implementation Teacher- (void)dealloc{    NSLog(@"叫%@的Teacher对象被销毁了",_teacherName);}@end/****************************** Student.h文件 ***********************************/#import <Foundation/Foundation.h>@class Teacher;@interface Student : NSObject@property (nonatomic,weak) Teacher *teahcher;@property (nonatomic,strong) NSStirng *studentName;@end/****************************** Student.m文件 ***********************************/#import "Student.h"#import "Teacher.h"@implementation Student- (void)dealloc{    NSLog(@"叫%@的Student对象被销毁了",_stuName);}@end/****************************** main.m文件 ***********************************/#import <Foundation/Foundation.h>#import "Teacher.h"#import "Student.h"int main(int argc, const char * argv[]){        Teacher *teacher = [[Teacher alloc] init];    teacher.teacherName  = @"张老师";        Student *student = [[Student alloc] init];    student.stuName = @"李同学";    　　// Student类对象中的Teacher属性为弱引用    student.teahcher = teacher;        // Teacher类对象中的Student属性为强引用    teacher.student = student;    return 0;}