How do I set bold and italic on UILabel of iPhone/iPad?

Question

Don't try to play with the font names. Using the font descriptor you need no names:

UILabel * label = [[UILabel alloc] init]; // use your label object instead of this
UIFontDescriptor * fontD = [label.font.fontDescriptor
            fontDescriptorWithSymbolicTraits:UIFontDescriptorTraitBold
                            | UIFontDescriptorTraitItalic];
label.font = [UIFont fontWithDescriptor:fontD size:0];

size:0 means 'keep the size as is'

With Swift try the following extension:

extension UIFont {

    func withTraits(traits:UIFontDescriptorSymbolicTraits...) -> UIFont {
        let descriptor = self.fontDescriptor()
            .fontDescriptorWithSymbolicTraits(UIFontDescriptorSymbolicTraits(traits))
        return UIFont(descriptor: descriptor, size: 0)
    }

    func boldItalic() -> UIFont {
        return withTraits(.TraitBold, .TraitItalic)
    }

}

Then you may use it this way:

myLabel.font = myLabel.font.boldItalic()

or even add additional traits like Condensed:

myLabel.font = myLabel.font.withTraits(.TraitCondensed, .TraitBold, .TraitItalic)

Update for Swift 4:

extension UIFont {
  var bold: UIFont {
    return with(traits: .traitBold)
  } // bold

  var italic: UIFont {
    return with(traits: .traitItalic)
  } // italic

  var boldItalic: UIFont {
    return with(traits: [.traitBold, .traitItalic])
  } // boldItalic


  func with(traits: UIFontDescriptorSymbolicTraits) -> UIFont {
    guard let descriptor = self.fontDescriptor.withSymbolicTraits(traits) else {
      return self
    } // guard

    return UIFont(descriptor: descriptor, size: 0)
  } // with(traits:)
} // extension

Use it as follows:

myLabel.font = myLabel.font.bold

or

myLabel.font = myLabel.font.italic

or

myLabel.font = myLabel.font.with(traits: [ .traitBold, .traitCondensed ])

Update for Swift 5

extension UIFont {
    var bold: UIFont {
        return with(.traitBold)
    }

    var italic: UIFont {
        return with(.traitItalic)
    }

    var boldItalic: UIFont {
        return with([.traitBold, .traitItalic])
    }



    func with(_ traits: UIFontDescriptor.SymbolicTraits...) -> UIFont {
        guard let descriptor = self.fontDescriptor.withSymbolicTraits(UIFontDescriptor.SymbolicTraits(traits).union(self.fontDescriptor.symbolicTraits)) else {
            return self
        }
        return UIFont(descriptor: descriptor, size: 0)
    }

    func without(_ traits: UIFontDescriptor.SymbolicTraits...) -> UIFont {
        guard let descriptor = self.fontDescriptor.withSymbolicTraits(self.fontDescriptor.symbolicTraits.subtracting(UIFontDescriptor.SymbolicTraits(traits))) else {
            return self
        }
        return UIFont(descriptor: descriptor, size: 0)
    }
}

sectionLabel.font = [UIFont fontWithName:@"TrebuchetMS-Bold" size:18];

There is a list of font names that you can set in place of 'fontWithName' attribute.The link is here

@Edinator have a look on this..

myLabel.font = [UIFont boldSystemFontOfSize:16.0f]
myLabel.font = [UIFont italicSystemFontOfSize:16.0f];

use any one of the above at a time you want

You can set any font style, family, size for the label, by clicking on letter "T" in Font field.

Swift 3

Bold:

let bondFont = UIFont.boldSystemFont(ofSize:UIFont.labelFontSize)

Italic:

let italicFont = UIFont.italicSystemFont(ofSize:UIFont.labelFontSize)

I have the same issue that need to apply both Bold and Italic on a label and button. You can simply use following code to achieve this effect:

myLabel.font = [UIFont fontWithName:@"Arial-BoldItalic" size:30.0];

With iOS 7 system default font, you'll be using helvetica neue bold if you are looking to keep system default font.

    [titleText setFont:[UIFont fontWithName:@"HelveticaNeue-Bold" size:16.0]];

Or you can simply call it:

    [titleText setFont:[UIFont boldSystemFontOfSize:16.0]];