iOS ARC下循環參考的問題

strong:適用於OC對象，作用和非ARC中的retain作用相同，它修飾的成員變數為強指標類型weak:適用於OC對象，作用和非ARC中的assign作用相同，修飾的成員變數為弱指標類型assging:適用於非OC物件類型 在OC對象循環參考的時候一端為strong類型，另一段為weak類型 範例程式碼如下：複製代碼複製代碼/****************************** Teacher.h檔案 ***********************************/#import <Foundation/Foundation.h>@class Student;@interface Teacher : NSObject@property (nonatomic,strong) Student *student;@property (nonatomic,strong) NSString *teacherName;@end /****************************** Teacher.m檔案 ***********************************/#import "Teacher.h"#import "Student.h"@implementation Teacher- (void)dealloc{    NSLog(@"叫%@的Teacher對象被銷毀了",_teacherName);}@end /****************************** Student.h檔案 ***********************************/#import <Foundation/Foundation.h>@class Teacher;@interface Student : NSObject@property (nonatomic,weak) Teacher *teahcher;@property (nonatomic,strong) NSStirng *studentName;@end  /****************************** Student.m檔案 ***********************************/#import "Student.h"#import "Teacher.h"@implementation Student- (void)dealloc{    NSLog(@"叫%@的Student對象被銷毀了",_stuName);}@end /****************************** main.m檔案 ***********************************/#import <Foundation/Foundation.h>#import "Teacher.h"#import "Student.h"int main(int argc, const char * argv[]){        Teacher *teacher = [[Teacher alloc] init];    teacher.teacherName  = @"張老師";        Student *student = [[Student alloc] init];    student.stuName = @"李同學";    　　// Student類對象中的Teacher屬性為弱引用    student.teahcher = teacher;        // Teacher類對象中的Student屬性為強引用    teacher.student = student;     return 0;}