//  main.m//  循环retain#import 
     
      #import "Person.h"#import "Dog.h"int main(int argc, const char * argv[]) {    Person *p = [Person new];    Dog *d = [Dog new];        // 如果A对用要拥有B对象, 而B对应又要拥有A对象, 此时会形成循环retain    // 如何解决这个问题: 不要让A retain B, B retain A    // 让其中一方不要做retain操作即可    p.dog = d; // retain    d.owner = p; // retain  assign        [p release];    [d release];        return 0;}
     

//  Dog.h#import 
     
      @class Person;@interface Dog : NSObject//@property(nonatomic, retain)Person *owner;@property(nonatomic, assign)Person *owner;@end
     

//  Dog.m#import "Dog.h"#import "Person.h"@implementation Dog-(void)dealloc{    NSLog(@"%s", __func__);//    [_owner release];//    self.owner = nil;    [super dealloc];}@end

////  Person.h#import 
     
      @class Dog;@interface Person : NSObject@property(nonatomic, retain)Dog *dog;@end
     

//  Person.m#import "Person.h"#import "Dog.h"@implementation Person- (void)dealloc{    NSLog(@"%s", __func__);//    [_dog release];    self.dog = nil;    [super dealloc];}@end