Replace font for every UILabel in the App - ios

Question

I'm trying to change the font by make extension for UILabel
extension UILabel{
var defaultFont: UIFont? {
get { return self.font }
set {
let oldFontSize = self.font.pointSize
let oldFontName = self.font.fontName
let newFontName = newValue?.fontName
self.font = UIFont(name: newFontName!, size: oldFontSize)
}
}
}
then call
UILabel.appearance().defaultFont = UIFont.init(name: "My Font", size: 5)
But always self.font is nil
using xcode 10 swift 4.2
Edit:
Now, after changing swift version to Swift3 it works good, then the problem is in Swift4.
Are there a solution or Alternative way to do that ?

Answer 1

try this :
is appDelegate -> didFinishLaunch:
UILabel.appearance().font = UIFont("your font name", size: 15)

Answer 2

Standard way of doing is to create your custom UILabel class and use this class everywhere you want that default font. e.g,
class MyFontLabel: UILabel {
override init(frame: CGRect) {
super.init(frame: frame)
self.commonInit()
}
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
self.commonInit()
}
private func commonInit() {
self.font = UIFont(name: "My Font", size: self.font.pointSize)
}
}

Answer 3

So while you technically can't override an instance variable, aka overriding UILabel's font variable won't work, you can extend UILabel.
public class CustomLabel: UILabel {
override public var font: UIFont! {
get { return super.font }
set {
super.font = UIFont(name: "Font-Name", size: super.font.pointSize)
}
}
}

Answer 4

I've found it most helpful to have add a style(as style: TypographyStyle) function in an extension to UILabel, where TypographyStyle is an enum I've defined that contains a bunch of style properties, including font. I also created a convenience init for UILabel that takes a case of TypographyStyle, and calls style(as:), so that the style will be automatically applied when the label is created.
extension UILabel {
convenience init(style: TypographyStyle) {
self.init()
self.style(as: style)
}
func style(as style: TypographyStyle) {
self.font = UIFont(name: style.fontName, size: style.fontSize)
}
}
enum TypographyStyle {
case body, h1, h2, h3
var font: UIFont {
switch self {
// here you can return different fonts for the different styles if you like
default:
return UIFont(name: "AvenirNext", size: 16)
}
}
}
// Usage
let label = UILabel(style: .body)

Answer 5

Put this on appDelegate in didFinishLaunchingWithOptions method:
UILabel.appearance().font = UIFont(name: "your font name", size: UILabel.appearance().font.pointSize)