NSString Quickies

Yet another small useful collection of small code snippets for NSString.


  • ‘join’ an array of strings into a single string
    NSArray *chunks  = ... get an array, say by splitting it;
    string = [chunks componentsJoinedByString: @" /// "];

    would produce something like

    oop /// ack /// bork /// greeble /// ponies
  • ‘split’ a string into an array
     NSString *string = @"oop:ack:bork:greeble:ponies";
    NSArray *chunks = [string componentsSeparatedByString: @":"];
  • Converting string to an integer
    NSString *string = ...;
    int value = [string intValue];

    Similarly, there is a floatValue and doubleValue NSString methods.

  • Iterating attributes in an attributed string
    This prints out each of the attribute runs from an attributed string:

    - (void) iterateAttributesForString: (NSAttributedString *) string
        NSDictionary *attributeDict;
        NSRange effectiveRange = { 0, 0 };
        do {
            NSRange range;
            range = NSMakeRange (NSMaxRange(effectiveRange),
                                 [string length] - NSMaxRange(effectiveRange));
            attributeDict = [string attributesAtIndex: range.location
                                    longestEffectiveRange: &effectiveRange
                                    inRange: range];
            NSLog (@"Range: %@  Attributes: %@",
                   NSStringFromRange(effectiveRange), attributeDict);
        } while (NSMaxRange(effectiveRange) < &#91;string length&#93;);
    } // iterateAttributesForString&#91;/sourcecode&#93;
    	<li><strong>Making localizable strings</strong>
    You will need a file named <code>Localizable.strings</code> that lives in your <code>English.lproj</code> directory (or whatever localization directory is appropriate). It has this syntax:
    "BorkDown" = "BorkDown";
    "Start Timer" = "Start Timer";
    "Stop Timer" = "Stop Timer";

    That is, a key followed by a localized value.In your code, you can then use NSLocalizedString() or one of its variants:

            [statusItem setTitle: NSLocalizedString(@"BorkDown", nil)];

    The second argument is ignored by the function. Obstensively it is a /* comment */ in the strings file so that you can match the key back to what it is supposed to actually be.

  • NSLog without the extra crud
    NSlog puts too much crud in front of the logging line. For a foundation tool that output stuff, it gets in the way. I’d still like for a replacement to expand %@, which the printf() family won’t do. Here’s a some code that’ll do that.

    #include <stdarg.h>
    void LogIt (NSString *format, ...)
        va_list args;
        va_start (args, format);
        NSString *string;
        string = [[NSString alloc] initWithFormat: format  arguments: args];
        va_end (args);
        printf ("%s\n", [string cString]);
        [string release];
    } // LogIt
  • Putting an image into an attributed string
    You’ll need to use a text attachment.

    - (NSAttributedString *) prettyName
        NSTextAttachment *attachment;
        attachment = [[[NSTextAttachment alloc] init] autorelease];
        NSCell *cell = [attachment attachmentCell];
        NSImage *icon = [self icon]; // or wherever you are getting your image
        [cell setImage: icon];
        NSString *name = [self name];
        NSAttributedString *attrname;
        attrname = [[NSAttributedString alloc] initWithString: name];
        NSMutableAttributedString *prettyName;
        prettyName = (id)[NSMutableAttributedString attributedStringWithAttachment:
                                                    attachment]; // cast to quiet compiler warning
        [prettyName appendAttributedString: attrname];
        return (prettyName);
    } // prettyName

    This puts the image at the front of the string. To put the image in the middle of the string, you’ll need to create an attributedstring with attachment, and then append that to your final attributed string.

  • Stripping out newlines from a string
    So you have an NSString and want to yank out the newlines. You can do a  split and join, like in scripting languages, or you can make a mutable copy and manipulate that:

        NSMutableString *mstring = [NSMutableString stringWithString:string];
        NSRange wholeShebang = NSMakeRange(0, [mstring length]);
        [mstring replaceOccurrencesOfString: @"
                 withString: @""
                 options: 0
                 range: wholeShebang];
        return [NSString stringWithString: mstring];

    (this can also be used for generic string manipulations, not just stripping out newlines).This technique takes half the time (at least) of split/join. But probably not enough to make an impact. In a simple test, split/join took 0.124 seconds to strip 36909 newlines in a 1.5 meg textfile, and 0.071 seconds to do the same.

  • Substring matching
    NSRange range = [[string name] rangeOfString: otherString options: NSCaseInsensitiveSearch];
  • Today’s date as a string
    The general solution for converting a date to a string is NSDateFormatter. Sometimes you need to generate a date string in a particular format easily. For instance if you need “December 4, 2007”, you can use:

    [[NSDate date] descriptionWithCalendarFormat: @"%B %e, %Y" timeZone: nil locale: nil]

    (Thanks to Mike Morton for this one)

  • Trimming whitespace from ends of a string
        NSString *ook = @"\n \t\t hello there \t\n  \n\n";
        NSString *trimmed =
            [ook stringByTrimmingCharactersInSet:
                     [NSCharacterSet whitespaceAndNewlineCharacterSet]];
        NSLog(@"trimmed: '%@'", trimmed);


    2009-12-24 18:24:42.431 trim[6799:903] trimmed: 'hello there'


  • Draw a string in bold
    - (void) drawLabel: (NSString *) label
               atPoint: (NSPoint) point
                  bold: (BOOL) bold {
        NSMutableDictionary *attributes = [NSMutableDictionary dictionary];
        NSFont *currentFont = [NSFont userFontOfSize: 14.0];
        if (bold) {
    	NSFontManager *fm = [NSFontManager sharedFontManager];
    	NSFont *boldFont = [fm convertFont: currentFont
                                   toHaveTrait: NSBoldFontMask];
    	[attributes setObject: boldFont
                        forKey: NSFontAttributeName];
        } else {
    	[attributes setObject: currentFont
                        forKey: NSFontAttributeName];
        [label drawAtPoint: point  withAttributes: attributes];;
    } // drawLabel


  • Put a string on the pasteboard
    Here’s a category for easily putting a string on the paste|clipboard:

    @implementation NSString (PasteboardGoodies)
    - (void) sendToPasteboard
            [[NSPasteboard generalPasteboard]
                declareTypes: [NSArray arrayWithObject: NSStringPboardType]
            [[NSPasteboard generalPasteboard]
                setString: self
                forType: NSStringPboardType];
    } // sendToPasteboard
    @end // PasteboardGoodies

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