UIFontDescriptor *helveticaNeueFamily =
[UIFontDescriptor fontDescriptorWithFontAttributes:
@{ UIFontDescriptorFamilyAttribute: @"Helvetica Neue" }];
NSArray *matches =
[helveticaNeueFamily matchingFontDescriptorsWithMandatoryKeys: nil];
The matchingFontDescriptorsWithMandatoryKeys: method as shown returns an array of font descriptors for all the Helvetica Neue fonts on the system, such as HelveticaNeue, HelveticaNeue-Medium, HelveticaNeue-Light, HelveticaNeue-Thin, and so on.
You can modify the fonts returned by preferredFontForTextStyle: by applying symbolic traits, such as bold, italic, expanded, and condensed. You can use font descriptors to modify particular traits, as shown in Listing 9-2.
referenced by apple
or
this font you can't apply directly.
so you can customize your font
How to use custom fonts in iPhone SDK?