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I have a string like 

 NSString * aString = @"\n    \n    \n   This is my string  ";

I need to extract firs blank spaces and new line characters upto first non-whitespace non-newline character. that is the output should be 

NSString *output = @"\n    \n    \n   ";

I tried it with NSScanner as follows NSString * aString = @"\n \n \n This is my string ";

NSScanner *scanner = [NSScanner scannerWithString:aString];
NSCharacterSet *characterSet = [[NSCharacterSet whitespaceAndNewlineCharacterSet] invertedSet];
NSString *output = nil;
[scanner scanUpToCharactersFromSet:characterSet intoString:&output];

But after execution the output string is nil. whats wrong with this code?

Johnykutty
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1 Answers1

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You can use regular expression to match all whitespaces (\s*) in the begining of the line (^):

NSString *string = @"\n    \n    \n   This is my string  ";
NSRegularExpression *expression = [[NSRegularExpression alloc] initWithPattern:@"^\\s*" options:0 error:NULL];
NSTextCheckingResult *match = [expression firstMatchInString:string options:0 range:NSMakeRange(0, string.length)];
NSString *output = [string substringWithRange:match.range];
ksysu
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  • Ok.. its working perfectly. Thank you for answer. Btw do you have any idea about what the problem with my NSScanner implementation? – Johnykutty Sep 02 '14 at 07:11
  • Also what I need to do for finding same from end of the striog? – Johnykutty Sep 02 '14 at 07:13
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    I tried to do something with your scanner, but I have no idea what is wrong there. You can use @"\\s*$" for finding same at the end ($ stands for end) – ksysu Sep 02 '14 at 07:36