How to return a value from Model to Controller using the [Swift5] protocol

Introduction

This article is a sequel to the previously posted ** [Swift5] How to communicate from a view controller to a Model and pass a value **. If you haven't seen it yet, I think it's better to see here ▼ first. https://qiita.com/nkekisasa222/items/dabe806c23d3890a009f

Let's get into the main subject!

Creating a protocol

First, write the code.

SampleModel.swift

//① Create a protocol here
protocol DoneCatchProtocol {
    
    //(2) Specify the value and type you want to return to Controller (String this time)
    func catchSampleData(sampleValueA: String, sampleValueB: String, sampleValueC: String)
}

class SampleModel {

    var sampleValueA: String?
    var sampleValueB: String?
    var sampleValueC: String?

    //③ Create an instance of the protocol
    var doneCatchProtocol: DoneCatchProtocol?

    init(firstSampleValue: String, secondSampleValue: String, thirdSampleValue: String) {

        sampleValueA = firstSampleValue
        sampleValueB = secondSampleValue
        sampleValueC = thirdSampleValue
    }

    //④ Create a method because processing is performed in Model
    func processingSampleModel {
    
        //⑤ Call the protocol created here and enter the value
        self.doneCatchProtocol?.catchSampleData(sampleValueA: sampleValueA, sampleValueB: sampleValueB, sampleValueC: sampleValueC)
    }

I will summarize the flow.

(1) Create a protocol on the Model side.
(2) Specify the key value and type of the value you want to return.
③ Create an instance of the protocol.
④ Create a method because processing is performed in Model
(5) Call the protocol and specify the value you want to call in Controller.

Description on the Controller side

First, write the code.

SampleViewController.swift

//(1) Call the Controller so that it can handle the protocol.
class SampleViewController: UIViewController, DoneCatchProtocol {

    firstSampleValue  = "firstSampleValue"
    secondSampleValue = "secondSampleValue"
    thirdSampleValue  = "thirdSampleValue"

    //④ Property to substitute the value returned from SampleModel
    var valueA: String?
    var valueB: String?
    var valueC: String?

    override func viewDidLoad() {
        super.viewDidLoad()

        startSampleModel()
    }

    func startSampleModel() {

      let sampleModel = SampleModel(firstSampleValue: firstSampleValue, secondSampleValue: secondSampleValue, thirdSampleValue: thirdSampleValue)

      //③ Entrust to SampleModel protocol and call method
      sampleModel.doneCatchProtocol = self
      sampleModel.processingSampleMode()
    }

    //(2) It is automatically generated when the protocol is called on the Controller side.
    func catchSampleData(sampleValueA: String, sampleValueB: String, sampleValueC: String) {

        //⑤ Substitute the value returned from SampleModel
        valueA = sampleValueA
        valueB = sampleValueB
        valueC = sampleValueC
    }
}

I will summarize the flow.

(1) Call the Controller so that it can handle the protocol.
(2) When the protocol is called in (1), the method is automatically generated.
③ Entrust to SampleModel protocol and call method
④ Prepare a property to substitute the value returned from SampleModel
⑤ Substitute the value returned from SampleModel

Now you can use the value processed by Model in Controller.

Finally

In the previous article and this article, I posted about how to communicate from Controller to Model, return the contents processed by Model to Controller, and handle it in Controller. Isn't it a development method that is often handled in the MVC model? I think that you can refer to it by all means.

Thank you for watching until the end!