Are there any analogues of [NSString stringWithFormat:] for NSAttributedString

Question

Usually I build app interface in interface builder. Sometimes design requires to use attributed strings (fonts, colors and etc.). It's easy to configure if string is static.
But if string is dynamic (format with arguments) then there are no ways to configure attributes in interface builder. It requires to write a lot of code.
I am looking for some analogues of [NSString stringWithFormat:] for NSAttributedString. So I will be able to set string format and necessary attributes in interface builder, and then provide necessary arguments in code.

For example:
Let's consider that I need display string with such format: "%d + %d = %d" (all numbers are bold).
I want to configure this format in interface builder. In code I want to provide arguments: 1, 1, 2. App should show "1 + 1 = 2".

Answer 1

Compatible with Swift 4.2

public extension NSAttributedString {
    convenience init(format: NSAttributedString, args: NSAttributedString...) {
        let mutableNSAttributedString = NSMutableAttributedString(attributedString: format)

        args.forEach { (attributedString) in
            let range = NSString(string: mutableNSAttributedString.string).range(of: "%@")
            mutableNSAttributedString.replaceCharacters(in: range, with: attributedString)
        }
        self.init(attributedString: mutableNSAttributedString)
    }
}

Usage:

let content = NSAttributedString(string: "The quick brown %@ jumps over the lazy %@")
let fox = NSAttributedString(string: "fox", attributes: [.font: Fonts.CalibreReact.boldItalic.font(size: 40)])
let dog = NSAttributedString(string: "dog", attributes: [.font: Fonts.CalibreReact.lightItalic.font(size: 11)])
attributedLabel.attributedText = NSAttributedString(format: content, args: fox, dog)

Result: