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    <p>I hate to throw another log on this exceptionally old fire, but I'm leery about editing someone else's answer - especially when it's the selected answer.</p> <p>Jacob asked a follow up question: How can I do this with a single method call?</p> <p>The answer is, by creating a category - which basically extends the functionality of a base Objective-C class - and writing a "shorthand" method for all the other code. </p> <p>However, technically, a string with white space characters is not empty - it just doesn't contain any visible glyphs (for the last couple of years I've been using a method called isEmptyString: and converted today after reading this question, answer, and comment set).</p> <p>To create a category go to Option+Click -> New File... (or File -> New -> File... or just command+n) -> choose Objective-C Category. Pick a name for the category (this will help namespace it and reduce possible future conflicts) - choose NSString from the "Category on" drop down - save the file somewhere. (Note: The file will automatically be named NSString+YourCategoryName.h and .m.)</p> <p>I personally appreciate the self-documenting nature of Objective-C; therefore, I have created the following category method on NSString modifying my original isEmptyString: method and opting for a more aptly declared method (I trust the compiler to compress the code later - maybe a little too much).</p> <p>Header (.h):</p> <pre><code>#import &lt;Foundation/Foundation.h&gt; @interface NSString (YourCategoryName) /*! Strips the string of white space characters (inlcuding new line characters). @param string NSString object to be tested - if passed nil or @"" return will be negative @return BOOL if modified string length is greater than 0, returns YES; otherwise, returns NO */ + (BOOL)visibleGlyphsExistInString:(NSString *)string; @end </code></pre> <p>Implementation (.m):</p> <pre><code>@implementation NSString (YourCategoryName) + (BOOL)visibleGlyphsExistInString:(NSString *)string { // copying string should ensure retain count does not increase // it was a recommendation I saw somewhere (I think on stack), // made sense, but not sure if still necessary/recommended with ARC NSString *copy = [string copy]; // assume the string has visible glyphs BOOL visibleGlyphsExist = YES; if ( copy == nil || copy.length == 0 || [[copy stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]] length] == 0 ) { // if the string is nil, no visible characters would exist // if the string length is 0, no visible characters would exist // and, of course, if the length after stripping the white space // is 0, the string contains no visible glyphs visibleGlyphsExist = NO; } return visibleGlyphsExist; } @end </code></pre> <p>To call the method be sure to #import the NSString+MyCategoryName.h file into the .h or .m (I prefer the .m for categories) class where you are running this sort of validation and do the following:</p> <pre><code>NSString* myString = @""; // or nil, or tabs, or spaces, or something else BOOL hasGlyphs = [NSString visibleGlyphsExistInString:myString]; </code></pre> <p>Hopefully that covers all the bases. I remember when I first started developing for Objective-C the category thing was one of those "huh?" ordeals for me - but now I use them quite a bit to increase reusability.</p> <p>Edit: And I suppose, technically, if we're stripping characters, this:</p> <pre><code>[[copy stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]] length] == 0 </code></pre> <p>Is really all that is needed (it should do everything that category method does, including the copy), but I could be wrong on that score.</p>
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    1. COI've now converted to just that one line instead of the category method in all my code - works as expected; so, no need to create extra code to maintain.
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