Reverse ViewModel

gistfile1.txt

// This is an experiment trying to understand how a reverse view model can be coded
//
// The inputView takes several inputs from the user and sends these to a delegate for further processing upon tapping a button
// the view model transforms the input strings to the correct type needed for the processing

// Approach inspired by http://matteomanferdini.com/mvvm-pattern-ios-swift/


// this struct should really be in the model, but is added here for brevity

struct Parameters {
    var string1: String
    var double1: Double
    var double2: Double
    var int1: Int
}

protocol InputViewDelegate: class {
    func process(_ params: Parameters?)
}

class InputView: UIView {
    @IBOutlet private weak var textView1: UITextView!
    @IBOutlet private weak var doubleTextField1: UITextField!
    @IBOutlet private weak var doubleTextField2: UITextField!
    @IBOutlet private weak var intTextField1: UITextField!
    
    var viewModel = ViewModel()

    weak var delegate: InputViewDelegate?
    
    @IBAction func processButtonTapped(_ sender: UIButton) {
        
        viewModel.string1 = self.textView1.text
        viewModel.doubleString1 = self.doubleTextField1.text! 
        viewModel.doubleString2 = self.doubleTextField2.text!
        viewModel.intString1 = self.intTextField1.text!
        
        self.delegate?.process(viewModel.parameters())
    }
}

extension InputView {
    struct ViewModel {
        let string1: String
        let doubleString1: String
        let doubleString2: String
        let intString1: String
    }
}

extension InputView.ViewModel {
    func parameters() -> Parameters 
        let params = Parameters(string1: self.string1,
                                double1: Double(self.double1)!,
                                double2: Double(self.double2)!,
                                int1: Int(self.int1)!)
        
        return params
    }
}