VFont

// First, you have to get information about the variable font (axes names, IDs, and allowed values). But the current axis value isn't there 🤷‍♂️
// Here you can face a problem, like the custom font wasn't added to the project, was added incorrectly, or font name isn't correct
let uiFont = UIFont(name: "Martian Mono", size: 16.0)!
let ctFont = CTFontCreateWithName(uiFont.fontName as CFString, 16.0, nil)
let variationAxes = CTFontCopyVariationAxes(ctFont) as! [Any] // font information with weird format 👎

// To set new values you need to know the correct axis IDs and allowed values (maxValue and minValue)
let variations = [2003265652: 600, 2003072104: 100] // 2003265652 - 'Weight'; 2003072104 - `Width`

// As we know, text elements in UIKit use the UIFont class. So, you have to create new UIFont object with new values for axes
let uiFontDescriptor = UIFontDescriptor(fontAttributes: [.name: uiFont.fontName, kCTFontVariationAttribute as UIFontDescriptor.AttributeName: variations])
let newUIFont = UIFont(descriptor: uiFontDescriptor, size: uiFont.pointSize) 
// Now, you can apply the UIFont object for UI text elements
// Here you may notice the name of the new UIFont object has been changed to 'MartianMono-Regular_wght2580000_wdth640000'
let label = UILabel()
label.font = newUIFont

import VFont

let vFont = VFont(name: "Martian Mono", size: 16)! // UIFont like initialization
vFont.setValue(400, forAxisID: 2003265652) // setting a new value for the 'Weight' axis

let label = UILabel()
label.font = vFont.uiFont // apply the variable font for a UI text element

vFont.getAxesDescription() // get the font information with а human readable format, if you need it ✅

// override the `updated` closure to observe all font changes, if you're going to change it at runtime
vFont.updated = { uiFont in
    label.font = uiFont
}

struct ContentView: View {

    var body: some View {
       Text("Title 1")
          .font(.vFont("Martian Mono", size: 16, axisID: 2003265652, value: 450))
       Text("Title 2")
           .font(.vFont("Inter", size: 32, axes: [2003072104: 80, 2003265652: 490])
    }
    
}

import VFont

final class MartianMono: VFont {
    
    init?(size: CGFloat) {
        super.init(name: "Martian Mono", size: size)
    }
    
    var weight: CGFloat {
        get {
            return axes[2003265652]?.value ?? .zero
        } set {
            setValue(newValue, axisID: 2003265652)
        }
    }
    
    var width: CGFloat {
        get {
            return axes[2003072104]?.value ?? .zero
        } set {
            setValue(newValue, axisID: 2003072104)
        }
    }
    
}

let font = MartianMono(size: 16)
        
font?.weight = 300
font?.width = 90

extension Font {
    
    static func martianMono(size: CGFloat, width: CGFloat = 0, weight: CGFloat = 0) -> Font {
        return .vFont("Martian Mono", size: size, axes: [
            2003072104: width,
            2003265652: weight
        ])
    }
    
}

struct ContentView: View {
    
    var body: some View {
        Text("Hello, world!")
            .font(.martianMono(size: 16, width: 300, weight: 100))
    }
    
}