Question

I’m looking to determine whether a string value from a user input (UITextField) is ‘blank’ if it’s not nil. Checking if [textField.text isEqualToString:''] isn’t quite enough because I want to avoid any blank/whitespace input (like say a few space characters).

There does seem to be an indication of a good solution for my particular problem in this StOv post.

Basically it goes something like this, but I suspect there has to (or ought to) be a better way:

NSString *strResult; NSScanner* scanner = [NSScanner scannerWithString:textField.text]; BOOL hasValidChars = [scanner scanUpToCharactersFromSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]                                               intoString:&strResult];  // if hasValidChars == YES, we've got nonwhite space chars collected into strResult 

This clearly only works for my particular circumstance, and even then it would fail if the first character was a space but the data I wanted followed. So, I realize I’ve been a little spoiled by Ruby, but there must be a tried and true idiom for trimming strings in Cocoa.

Aaaand the answer is already out there, my apologies:

NSString’s -stringByTrimmingCharactersInSet: would do it:

Returns a new string made by removing from both ends of the receiver characters contained in a given character set.

I’m still curious to hear if anybody has other/preferred ways of doing this.

Answer 1

You’re using whitespaceAndNewlineCharacterSet, good. But instead of using scanUpToCharactersFromSet, why not use stringByTrimmingCharactersInSet? Something like this…

strResult = [strResult stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]]; 

EDIT: Didn’t realize you already found stringByTrimmingCharactersInSet until after I posted this.