How to use NSScanner? - objective-c

Question

I've just read Apple documentation for NSScanner.
I'm trying to get the integer of this string:
#"user logged (3 attempts)"
I can't find any example, how to scan within parentheses. Any ideas?
Here's the code:
NSString *logString = #"user logged (3 attempts)";
NSScanner *aScanner = [NSScanner scannerWithString:logString];
[aScanner scanInteger:anInteger];
NSLog(#"Attempts: %i", anInteger);

Answer 1

Ziltoid's solution works, but it's more code than you need.
I wouldn't bother instantiating an NSScanner for the given situation. NSCharacterSet and NSString give you all you need:
NSString *logString = #"user logged (3 attempts)";
NSString *digits = [logString stringByTrimmingCharactersInSet:
[[NSCharacterSet decimalDigitCharacterSet] invertedSet]];
NSLog(#"Attempts: %i", [digits intValue]);
or in Swift:
let logString = "user logged (3 attempts)"
let nonDigits = NSCharacterSet.decimalDigitCharacterSet().invertedSet
let digits : NSString = logString.stringByTrimmingCharactersInSet(nonDigits)
NSLog("Attempts: %i", digits.intValue)

Answer 2

`Here is what I do to get certain values out of a string
First I have this method defined
- (NSString *)getDataBetweenFromString:(NSString *)data leftString:(NSString *)leftData rightString:(NSString *)rightData leftOffset:(NSInteger)leftPos;
{
NSInteger left, right;
NSString *foundData;
NSScanner *scanner=[NSScanner scannerWithString:data];
[scanner scanUpToString:leftData intoString: nil];
left = [scanner scanLocation];
[scanner setScanLocation:left + leftPos];
[scanner scanUpToString:rightData intoString: nil];
right = [scanner scanLocation] + 1;
left += leftPos;
foundData = [data substringWithRange: NSMakeRange(left, (right - left) - 1)]; return foundData;
}
Then call it.
foundData = [self getDataBetweenFromString:data leftString:#"user logged (" rightString:#"attempts)" leftOffset:13];
leftOffset is the number of characters for the left string
Could be an easier cleaner way but that was my solution.

Answer 3

Here is a simple solution using NSScanner (yes, #NSResponder has a really neat solution!):
NSString *logString = #"user logged (3 attempts)";
NSString *numberString;
NSScanner *scanner = [NSScanner scannerWithString:logString];
[scanner scanUpToCharactersFromSet:[NSCharacterSet decimalDigitCharacterSet] intoString:nil];
[scanner scanCharactersFromSet:[NSCharacterSet decimalDigitCharacterSet] intoString:&numberString];
NSLog(#"Attempts: %i", [numberString intValue]);
NSLog output:
Attempts: 3

Answer 4

NSScanner is a linear scanner. You have to scan through the stuff you don't want to get to what you do want.
You could do [aScanner scanUpToCharactersInSet:[NSCharacterSet decimalDigitCharacterSet] intoString:NULL] to jump past everything up to the number character. Then you do [aScanner scanInteger:&anInteger] to scan the character into an integer.

Answer 5

here is the reg-ex usage
NSString *logString = #"user logged (3 attempts)";
NSString * digits = [logString stringByMatching:#"([+\\-]?[0-9]+)" capture:1];