First code and output: 

NSString *text = @"Sunny";
__weak NSString *string0 = text.lowercaseString;
__weak NSString *string1;
string1 = text.lowercaseString;
 
NSLog(@"%@, %@", string0, string1);

 Output: 

(null), sunny

But after I move the declaration of string1 above the text, output is different. Here is the code: 

__weak NSString *string1;
NSString *text = @"Sunny";
__weak NSString *string0 = text.lowercaseString;
string1 = text.lowercaseString;
 
NSLog(@"%@, %@", string0, string1);

 Output: 

sunny, sunny

I am very confused with the different output:

·         Why string0 and string1 is different in the first case?

·         Why the output of second case is different with the first?