Change default system font in SwiftUI

Question

I'm trying to set a custom default font in my SwiftUI app. I tried several suggestions from this thread Set a default font for whole iOS app?.

However, none of those seem to work with SwiftUI. For example with this approach:

// Constants.swift
struct Fonts {
    static var plex = "IBMPlexMono-Text"
}


// FontExtension.swift
extension UILabel {
    var substituteFontName : String {
        get { return self.font.fontName }
        set { self.font = UIFont(name: Fonts.plex, size: 17)! }
    }

}

// AppDelegate.swift in didFinishLaunchingWithOptions-function
UILabel.appearance().substituteFontName = Fonts.plex

When I start the app, the custom font appears for a split second and then changes back to the default font by Apple. Why does it change back to Apple's font and how can it be done permanently?

Is it maybe possible with an extension on Text-View?

Answer 1

You can have:

extension Font {
    static let mediumFont = Font.custom("Sans-Regular", size: Font.TextStyle.subheadline.size, relativeTo: .caption)
    static let mediumSmallFont = Font.custom("Sans-Regular", size: Font.TextStyle.footnote.size, relativeTo: .caption)
    static let smallFont = Font.custom("Sans-Regular", size: Font.TextStyle.caption.size, relativeTo: .caption)
    static let verySmallFont = Font.custom("Sans-Regular", size: Font.TextStyle.caption2.size, relativeTo: .caption)
}

extension Font.TextStyle {
    var size: CGFloat {
        switch self {
        case .largeTitle: return 60
        case .title: return 48
        case .title2: return 34
        case .title3: return 24
        case .headline, .body: return 18
        case .subheadline, .callout: return 16
        case .footnote: return 14
        case .caption: return 12
        case .caption2: return 10
        @unknown default:
            return 8
        }
    }
}

and use it like this:

Text("Edit Profile")
   .font(.mediumSmallFont)