A UIImage category class method for drawing icon font ligatures to images

gistfile1.m

+ (UIImage *)iconWithFont:(UIFont *)font named:(NSString *)iconNamed forSize:(CGFloat)fontSize{
    static NSCache *cache = nil;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        cache = [[NSCache alloc] init];
    });

    NSString *identifier = [NSString stringWithFormat:@"%@%@%f", font.fontName, iconNamed, fontSize];
    UIImage *image = [cache objectForKey:identifier];
    if(image == nil){
        NSMutableAttributedString *ligature = [[NSMutableAttributedString alloc] initWithString:iconNamed];
        [ligature setAttributes:@{(NSString *)kCTLigatureAttributeName:@(2),
         (NSString *)kCTFontAttributeName:font} range:NSMakeRange(0, [ligature length])];
        
        CGSize iconSize = [ligature size];
        iconSize.width = ceil(iconSize.width);
        iconSize.height = ceil(iconSize.height);
        if(!CGSizeEqualToSize(CGSizeZero, iconSize)){
            UIGraphicsBeginImageContextWithOptions(iconSize, NO, 0);
            [[UIColor blackColor] setFill];
            [ligature drawAtPoint:CGPointZero];
            image = UIGraphicsGetImageFromCurrentImageContext();
            UIGraphicsEndImageContext();
            
            [cache setObject:image forKey:identifier];
        }
    }
    return image;
}