Loop reference in iOS ARC

Strong: applies to OC objects. It acts the same as retain in non-ARC objects. Its Modified member variables are strongly pointer-type weak: applies to OC objects and works the same as assign in non-ARC objects, modified member variables are weak pointer type assging: applicable to non-OC object types. When the OC object is referenced cyclically, one end is of the strong type, and the other is of the weak type. The sample code is as follows: copy the code to copy the code/******************************* Teacher. h file ***********************************/# import <Foundation/Foundation. h> @ class Student; @ interface Teacher: NSObject @ property (nonatomic, strong) Student * student; @ property (nonatomic, strong) NSString * teacherName; @ end/******************************* Teacher. m file **********************************/# import "Teacher. h "# import" Student. h "@ implementation Teacher-(void) dealloc {NSLog (@" the Teacher object named % @ has been destroyed ", _ teacherName );} @ end/******************************** Student. h file ***********************************/# import <Foundation/Foundation. h> @ class Teacher; @ interface Student: NSObject @ property (nonatomic, weak) Teacher * teahcher; @ property (nonatomic, strong) NSStirng * studentName; @ end/******************************** Student. m file **********************************/# import "Student. h "# import" Teacher. h "@ implementation Student-(void) dealloc {NSLog (@" Student object named % @ has been destroyed ", _ stuName );} @ end/******************************* main. m file **********************************/# import <Foundation/Foundation. h> # import "Teacher. h "# import" Student. h "int main (int argc, const char * argv []) {Teacher * teacher = [[Teacher alloc] init]; teacher. teacherName = @ "instructor Zhang"; Student * student = [[Student alloc] init]; student. stuName = @ "Li "; // The Teacher attribute in the Student Class Object is weak reference student. teahcher = teacher; // The Student attribute in the Teacher Class Object is strongly referenced by teacher. student = student; return 0 ;}