NSString *str = @“lanou”; [str retain]; NSLog(@“%lu”,str.retainCount);
1
2
-1
ULONG_MAX
NSString *str = @"xxxx"; [str retain]; NSLog(@"%ld",str.retainCount);// -1
NSString *str = @"xxxx"; [str retain]; NSLog(@"%lu",str.retainCount); //18446744073709551615
%lu无符号长整形 %ld 长整型
%ld 长整型
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