How can I use NSError in my iPhone App?

Question

I am working on catching errors in my app, and I am looking into using NSError. I am slightly confused about how to use it, and how to populate it.

Answer 1

extension NSError {
    static func defaultError() -> NSError {
        return NSError(domain: "com.app.error.domain", code: 0, userInfo: [NSLocalizedDescriptionKey: "Something went wrong."])
    }
}

which I can use NSError.defaultError() whenever I don't have valid error object.

let error = NSError.defaultError()
print(error.localizedDescription) //Something went wrong.