IOS @proporty 关键字（一）retain strong

最新推荐文章于 2021-09-04 11:53:18 发布

weixin_30852419

最新推荐文章于 2021-09-04 11:53:18 发布

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CC 4.0 BY-SA版权

原文链接：http://www.cnblogs.com/FlyLolo/p/7128494.html

本文探讨了Objective-C中ARC（自动引用计数）的使用，重点分析了对象的引用计数变化及其对内存管理的影响。

@interface User : NSObject  
  
@property (nonatomic,retain) NSString* tRetain;  
@property (nonatomic,assign) NSString* tAssign;  
@property (nonatomic,copy) NSString* tcopy;  
  
@end

类User有个属性tRetain, 只是测试就用NSString类型了（此类型一般用copy, 因为可能是个NSMutableString,不希望在赋值后被其他地方修改内容）。

User* user = [[User alloc]init];  
  
NSString* testRetain = [NSString stringWithFormat:@"retain"];  
NSLog(@"testRetain.retainCount=%lu",(unsigned long)testRetain.retainCount);  //1  
  
user.tRetain = testRetain;  
NSLog(@"testRetain.retainCount=%lu",(unsigned long)testRetain.retainCount);   //2  
NSLog(@"user.tRetain.retainCount=%lu",(unsigned long)user.tRetain.retainCount); //2  
  
NSString* testRetain2 = @"retain2";  
NSLog(@"testRetain2.retainCount=%lu",(unsigned long)testRetain2.retainCount); //4294967295 自动释放对象  返回max unsigned long  
  
  
user.tRetain = testRetain2;  
NSLog(@"testRetain.retainCount=%lu",(unsigned long)testRetain.retainCount);   //1  
NSLog(@"testRetain2.retainCount=%lu",(unsigned long)testRetain2.retainCount); //4294967295  
NSLog(@"user.RetainValue.retainCount=%lu",(unsigned long)user.tRetain.retainCount); //4294967295  
  
  
NSString* testRetain3 = [NSString stringWithFormat: @"retain3"];  
NSLog(@"testRetain3.retainCount=%lu",(unsigned long)testRetain3.retainCount); //1  
  
[testRetain3 retain];  
NSLog(@"testRetain3.retainCount=%lu",(unsigned long)testRetain3.retainCount); //2  
  
NSString* testRetain4 = [NSString stringWithString:testRetain3];  
NSLog(@"testRetain3.retainCount=%lu",(unsigned long)testRetain3.retainCount); //3  
NSLog(@"testRetain4.retainCount=%lu",(unsigned long)testRetain4.retainCount); //3