Gives the height an NSAttributedString will take up when constrained to a given width.

NSAttributedString+height.h

#import <CoreText/CoreText.h>

@interface NSAttributedString (Height)
-(CGFloat)boundingHeightForWidth:(CGFloat)inWidth;
@end

NSAttributedString+height.m

#import "NSAttributedString+height.h"

@implementation NSAttributedString (Height)
- (CGFloat)boundingHeightForWidth:(CGFloat)inWidth {
    CGFloat height = 0;

    CTFramesetterRef framesetter = CTFramesetterCreateWithAttributedString ( (CFMutableAttributedStringRef) self);
    CGRect box = CGRectMake(0,0, inWidth, CGFLOAT_MAX);

    CFIndex startIndex = 0;

    CGMutablePathRef path = CGPathCreateMutable(); 
    CGPathAddRect(path, NULL, box);

    CTFrameRef frame = CTFramesetterCreateFrame(framesetter, CFRangeMake(startIndex, 0), path, NULL);

    CFArrayRef lineArray = CTFrameGetLines(frame); 
    CFIndex j = 0, lineCount = CFArrayGetCount(lineArray); 
    CGFloat lineHeight, ascent, descent, leading;

    for (j=0; j < lineCount; j++) {
        CTLineRef currentLine = (CTLineRef)CFArrayGetValueAtIndex(lineArray, j);
        CTLineGetTypographicBounds(currentLine, &ascent, &descent, &leading);      
        lineHeight = ascent + descent + leading;
        height += lineHeight;
    }

    CFRelease(frame);
    CFRelease(path);
    CFRelease(framesetter);

    return height;
}

@end