Set Specific Font Weight for UILabel in Swift

Question

When people have asked how to set a bold font, most people suggest:

let boldFont = UIFont.boldSystemFont(ofSize: ___)

But take a look at all the font weights that the standard system font offers:

So my question is how do you set a light, semibold, or heavy font weight? The only way that I know how is:

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

However, I'm still asking because this isn't strongly typed. Most other class attributes are set by selecting from a fixed set of options and don't require passing a string that I could mistype. I guess I could set my own global enum... But any better ideas?

`class func systemFont(ofSize fontSize: CGFloat, weight: UIFont.Weight) -> UIFont` — Leo Dabus, Feb 19 '18 at 03:03
You can use the initializer above and choose any font weight. i.e: `let systemFont: UIFont = .systemFont(ofSize: 32, weight: .thin)` — Leo Dabus, Feb 19 '18 at 03:03
@rmaddy there is only one bold option in font descriptor `UIFontDescriptorSymbolicTraits.traitBold` — Leo Dabus, Feb 19 '18 at 03:15
Possible duplicate of [How do I create a bold UIFont from a regular UIFont?](https://stackoverflow.com/questions/16015916/how-do-i-create-a-bold-uifont-from-a-regular-uifont) — BB9z, Nov 28 '18 at 06:05
Hi, I'm the author of the suggested duplicate question here. I don't think this question is a duplicate of the [other question](https://stackoverflow.com/q/16015916/754705). I posted my reasoning in the comments on the other question. — Michael, Nov 28 '18 at 15:46

score 31 · Accepted Answer · answered Feb 19 '18 at 03:32

31

I couldn't get the UIFontDescriptor to work with the font weight trait but there is another approach.

let font = UIFont.systemFont(ofSize: 20, weight: .light)

Replace .light with whichever value you want from UIFont.Weight which basically matches the dropdown list shown in your question.

answered Feb 19 '18 at 03:32

rmaddy

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How to change font weight of a custom font programmatically ? – Awais Fayyaz Jul 08 '19 at 07:44
`UILable.font = UIFont(name: "MarkerFelt-Thin", size: 16)` just put `bold` or `thin` etc after the font name. – Zhou Haibo Nov 04 '20 at 16:41
How can we set the weight of a custom font without changing it the system one?, I'm using Roboto Flex which is a variable font. – vhugo Jul 07 '22 at 12:09

score 18 · Answer 2 · answered Apr 06 '20 at 15:24

18

You can use this extension. It assigns the weight to the fontDescriptor's weight key and instantiate your font with this new descriptor.

extension UIFont {
  func withWeight(_ weight: UIFont.Weight) -> UIFont {
    let newDescriptor = fontDescriptor.addingAttributes([.traits: [
      UIFontDescriptor.TraitKey.weight: weight]
    ])
    return UIFont(descriptor: newDescriptor, size: pointSize)
  }
}

answered Apr 06 '20 at 15:24

arvinq

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This is not work for getting a regular weight font from a bold font, it still shows bold after adding regular weight trait. Test with New York font. – zgjie Nov 20 '21 at 09:58
Test with New York and San Francisco Rounded fonts. It seems this only works for San Francisco font. – zgjie Nov 20 '21 at 10:04

Krzysztof Skrzynecki · Answer 3 · 2020-02-20T09:13:53.447

6

The very old thread, but someone may be interested in how to do it in Swift.

UIFont.Weight defines all of the options:

ultraLight
thin
light
regular
medium
semibold
bold
heavy
black

you can use simply like that, e.g.:

label.font = UIFont.systemFont(ofSize: size, weight: .bold)

or if you want to keep the previous size:

label.font = UIFont.systemFont(ofSize: label.font!.pointSize, weight: .bold)

edited Feb 20 '20 at 09:13

answered Feb 20 '20 at 09:04

Krzysztof Skrzynecki

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Buhaescu Vlad · Answer 4 · 2019-11-05T10:42:24.387

1

Even more:

let font = UIFont.systemFont(ofSize: 20, weight: UIFont.Weight(500))

edited Nov 05 '19 at 10:42

answered Nov 04 '19 at 18:05

Buhaescu Vlad

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The iOS font weight is on a scale of -1 to 1, so this would return the heaviest possible font weight. – Nathan Dudley May 13 '20 at 22:36

score 0 · Answer 5 · answered Nov 13 '22 at 12:49

0

If you want to use system fonts, for Swift 5 a simple extension would look like this:

extension UIFont {
    func withWeight(_ weight: UIFont.Weight) -> UIFont {
        UIFont.systemFont(ofSize: pointSize, weight: weight)
    }
}

answered Nov 13 '22 at 12:49

CristianMoisei

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Set Specific Font Weight for UILabel in Swift

5 Answers5