Hands-On Design Patterns with Swift

Model controllers

The next step is to extract validation and networking logic into their own controllers. That way, we can easily extend their features, while maintaining a simple API surface:

class PostMessageNetworking {    func post(message: String,              callback: @escaping (Bool, Error?) ->  Void) {        /* original call */    }}class MessageValidator {    enum ValidationError: Error {    case emptyMessage    }        func validate(message: String) -> ValidationError? {        if message.count == 0 {            return .emptyMessage        }        return nil    }}

We extracted both features, validation and networking, into two independent controllers for the model layer. As you can see, none of them interact with the view layer. Their interfaces are simple: one has a callback, the other returns an optional ...