Decouple UI from Model with View Models and Controls question. http://christiantietze.de/posts/2015/10/view-model-control/

example.swift

class NetworkController {

    // To simplify getSomeDataFromNetwork() send request synchronously 
    // and return a value on success, .None on failure.
    func getSomeDataFromNetwork() -> AnyObject? {}
}

struct ViewModel {

    var networkController: NetworkController

    var error = false
    var data = "A default value"

    init() {
        networkController = NetworkController()
        refreshServerState()
    }

    mutating func refreshServerState() {
        if let newData = networkController.getSomeDataFromNetwork() {
            data = String(newData)
        } else {
            error = true
        }
    }
}

// My problem with having a copy of ViewModel in Presenter and ViewController:
//
// Your Presenter need to refresh server state every X minutes to update its views and your ViewController
// need to know if the request encounter an error to push an error view controller But each one has a 
// different copy of ViewModel :( so they have to perform their own request.