Using custom font in iOS without register to Info.plist

FontLoader.swift

public class FontLoader {
    private enum Error: Swift.Error {
        case error(String)
    }
    
    /// Register fonts
    ///
    /// - Parameter fonts: Font names
    static func registerFonts(fonts: [String]) throws {
        let bundle = Bundle(for: FontLoader.self)
        let urls = fonts.compactMap({ bundle.url(forResource: $0, withExtension: "ttf") })
        try urls.forEach { (url) in
            let data = try Data.init(contentsOf: url)
            guard let provider = CGDataProvider.init(data: data as CFData) else { throw Error.error("CGDataProvider nil") }
            guard let font = CGFont.init(provider) else { throw Error.error("CGFont nil") }
            var error: Unmanaged<CFError>?
            guard CTFontManagerRegisterGraphicsFont(font, &error) else {
                throw error!.takeUnretainedValue()
            }
        }
    }
}

Getting actual error. duplicateName or alreadyRegistered error is common. direct casting from cfError to NSError doesn't work, we first need to cast to Error.
let cfError = error?.takeRetainedValue() if let err = (cfError as? Error) as? NSError { if err.code == CTFontManagerError.alreadyRegistered.rawValue || err.code == CTFontManagerError.duplicatedName.rawValue { } }

Thanks. Why does that error happen? Do you install different font using similar name as system provided one?

Yes. I'm loading a many fonts from server, synching them locally and loading in table view cell from file url. Table cell registers font which caused the issue.

I would suggest to filter those fonts before register them. Or you can handle that for your specific use case.

The error is alreadyRegistered, not duplicate. As table view reloads cells, it reloads font from url and registers it to output ui font. Is there an other way to check already registered font? Thanks.