IOS@proportyキーワード(一)retain strong

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

クラスUserには属性tRetainがあり、テストだけでNSStringタイプを使用します(このタイプは一般的にcopyを使用します.NSMutablesStringである可能性があるので、割り当て後に他の場所で内容を変更したくない).

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     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  

strongはARC後に導入されたキーワードであり,ARC環境ではRetainと同等である.
 
NSSring*str=[NSString stringWithString:文字列];この方法は、retainプロパティに前述した値を割り当てることに相当します.後続の文字列パラメータのカウントが4294967295の場合、strのカウントもです.文字列パラメータがカウント可能である、例えば1であれば、実行後のカウントに1を加算.