摘要：
NSString *a = [[NSString alloc]initWithString:@"hello"]; NSString *b = [a copy]; NSLog(@"%d %d",a.retainCount, b.retainCount);// 2，2 NSMutableString *f = [a mutableCopy]; NSLog(@"%d %d",a.retainCount, f.retainCount);// 2，1 [f appendString:@"dd"]; NSLog(@" 阅读全文
