Convert from SwiftUI.Font to UIFont

Question

I have a UIViewRepresentable with a UITextView and I want to set the font on the UITextView using the current Font from the SwiftUI environment. I just need a simple init like:

UIFont(_ swiftUIFont: Font)

But I can't find any such thing. And the Font type doesn't seem to have any information I can use to try to implement one. Anyone know of a way to convert between the two font representations?

unfortunately, not yet (at least, I didn't find any way), fill the radar ... — user3441734
– user3441734, Commented Feb 4, 2020 at 10:27
Keep in mind: SwiftUI.Font is a View, where UITextView.font is a UIFont — nine stones
– nine stones, Commented Feb 7, 2020 at 17:39
@ninestones SwiftUI.Font is just a plain Struct conforms to Equatable and Hashable, not a View: developer.apple.com/documentation/swiftui/font — Jonny
– Jonny, Commented Jun 27, 2020 at 6:23
github.com/LeoNatan/LNSwiftUIUtils I've created a small library, which includes a Font -> UIFont conversion method. It supports all modifiers but the leading() one. — Léo Natan
– Léo Natan, Commented Oct 22, 2023 at 17:49

Luke Howard · Accepted Answer · 2021-01-30 11:43:18Z

19

A bit of a hack but works (doing the other direction is left as an exercise to the reader).

extension UIFont {
    class func preferredFont(from font: Font) -> UIFont {
        let uiFont: UIFont
        
        switch font {
        case .largeTitle:
            uiFont = UIFont.preferredFont(forTextStyle: .largeTitle)
        case .title:
            uiFont = UIFont.preferredFont(forTextStyle: .title1)
        case .title2:
            uiFont = UIFont.preferredFont(forTextStyle: .title2)
        case .title3:
            uiFont = UIFont.preferredFont(forTextStyle: .title3)
        case .headline:
            uiFont = UIFont.preferredFont(forTextStyle: .headline)
        case .subheadline:
            uiFont = UIFont.preferredFont(forTextStyle: .subheadline)
        case .callout:
            uiFont = UIFont.preferredFont(forTextStyle: .callout)
        case .caption:
            uiFont = UIFont.preferredFont(forTextStyle: .caption1)
        case .caption2:
            uiFont = UIFont.preferredFont(forTextStyle: .caption2)
        case .footnote:
            uiFont = UIFont.preferredFont(forTextStyle: .footnote)
        case .body:
            fallthrough
        default:
            uiFont = UIFont.preferredFont(forTextStyle: .body)
        }
        
        return uiFont
    }
}

edited Jan 30, 2021 at 11:43

answered Oct 22, 2020 at 23:01

Luke Howard

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3 Comments

David James Over a year ago

This does not support custom font designs (rounded, etc), custom sizes/weights or custom fonts. I suggest people create feedbacks for Apple to support retrieving a UIFont or NSFont instance from Font directly.

David James Over a year ago

@Luke_Howard perhaps change the method name to preferredFont(from font:Font) to reflect that this only returns default system font.

RobMac Over a year ago

I don't think that this answers the OP's question. There's the assumption of using the default font. What if the OP loaded a custom font?

MarkAurelius · Accepted Answer · 2023-10-04 05:08:15Z

16

Here is a reformatting of Luke Howard's solution to reduce the amount of text

extension UIFont {
  class func preferredFont(from font: Font) -> UIFont {
      let style: UIFont.TextStyle
      switch font {
        case .largeTitle:  style = .largeTitle
        case .title:       style = .title1
        case .title2:      style = .title2
        case .title3:      style = .title3
        case .headline:    style = .headline
        case .subheadline: style = .subheadline
        case .callout:     style = .callout
        case .caption:     style = .caption1
        case .caption2:    style = .caption2
        case .footnote:    style = .footnote
        case .body: fallthrough
        default:           style = .body
     }
     return  UIFont.preferredFont(forTextStyle: style)
   }
}

From Swift 5.9, you can use the switch statement to return a value and have an even less cluttered look:

extension UIFont {
  class func preferredFont(from font: Font) -> UIFont {
      let style: UIFont.TextStyle =
      switch font {
        case .largeTitle:   .largeTitle
        case .title:        .title1
        case .title2:       .title2
        case .title3:       .title3
        case .headline:     .headline
        case .subheadline:  .subheadline
        case .callout:      .callout
        case .caption:      .caption1
        case .caption2:     .caption2
        case .footnote:     .footnote
        default: /*.body */ .body 
      }
      return  UIFont.preferredFont(forTextStyle: style)
    }
 }

edited Oct 4, 2023 at 5:08

answered Mar 21, 2022 at 5:25

MarkAurelius

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3 Comments

Grimxn Over a year ago

Nice piece of re-factoring.

Grimxn Over a year ago

Note that this works equally well for NSFont.

MarkAurelius Over a year ago

I have added a version that works with the new syntax feature in Swift 5.9, of allowing switch to return a value

lennartk · Accepted Answer · 2023-11-05 13:44:50Z

5

It's a good question and although as mentioned in the other answers, you can't convert SwiftUI.Font directly to UIFont, but you can easily work around it by using Foundation's AttributedString. Here's how I did it for UILabel:

func updateUIView(_ label: UILabel, context: Context) {
    var container = AttributeContainer()
    container.font = context.environment.font

    let attributedString = AttributedString(text, attributes: container)
    label.attributedText = NSAttributedString(attributedString)
}

answered Nov 5, 2023 at 13:44

lennartk

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4 Comments

David J. Over a year ago

(A) I'm not following how this addresses the question of finding a UIFont that corresponds to a given SwiftUI.Font. (B) It sounds like you provided a workaround, but I'm not seeing the connection yet. Could you flesh out your explanation please?

lennartk Over a year ago

Hey @DavidJ. you're right. I tried to give an answer to the question, which was about using it in a UIViewRepresentable with UITextView. You could perhaps (ab)use the AttributeContainer to convert between the two by using the swiftUI and uiKit atributes on that container: developer.apple.com/documentation/foundation/attributescopes

MarK Over a year ago

This doesn't work. The font in attributes of NSAttributedString remainsFont.

lennartk Over a year ago

@MarK perhaps you could first convert it to NSAttributedString and read it from there? It should only support UIFont.

JIE WANG · Accepted Answer · 2020-09-21 22:10:38Z

3

No you can't, you have to use the params you passed to the Font to create UIFont

answered Sep 21, 2020 at 22:10

JIE WANG

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