ios - How do I create a bold UIFont from a regular UIFont?

Question

If I have a UIFont object, is it possible to convert it to bold? I don't know the font name, I just have a UIFont object. What I want is a function like

UIFont *boldFontFromFont(UIFont *input)
{
    return [input derivedFontWithFontWeight:UIFontWeightBold];
}

How can I change the code so that it works. (The code above does not work, I just made it up to illustrate the point.)

Thanks in advance.

Answer 1

iOS 7 introduces a new UIFontDescriptor class, which makes it a lot easier:

UIFont *font = [UIFont fontWithName:@"Helvetica Neue" size:12];
NSLog(@"plain font: %@", font.fontName); // “HelveticaNeue”

UIFont *boldFont = [UIFont fontWithDescriptor:[[font fontDescriptor] fontDescriptorWithSymbolicTraits:UIFontDescriptorTraitBold] size:font.pointSize];
NSLog(@"bold version: %@", boldFont.fontName); // “HelveticaNeue-Bold”

UIFont *italicFont = [UIFont fontWithDescriptor:[[font fontDescriptor] fontDescriptorWithSymbolicTraits:UIFontDescriptorTraitItalic] size:font.pointSize];
NSLog(@"italic version: %@", italicFont.fontName); // “HelveticaNeue-Italic”

UIFont *boldItalicFont = [UIFont fontWithDescriptor:[[font fontDescriptor] fontDescriptorWithSymbolicTraits:UIFontDescriptorTraitBold | UIFontDescriptorTraitItalic] size:font.pointSize];
NSLog(@"bold & italic version: %@", boldItalicFont.fontName); // “HelveticaNeue-BoldItalic”

For people who got here looking for a Cocoa (macOS) equivalent, UIFontDescriptor comes from NSFontDescriptor, available since 10.3.