SwiftUI: Forcing an Update

2021 SWIFT 1 and 2 both:

IMPORTANT THING! If you search for this hack, probably you doing something wrong! Please, read this block before you read hack solution!!!!!!!!!!

Your UI wasn't updated automatically because of you miss something important.

• Your ViewModel must be a class wrapped into ObservableObject/ObservedObject
• Any field in ViewModel must be a STRUCT. NOT A CLASS!!!! Swift UI does not work with classes!
• Must be used modifiers correctly (state, observable/observedObject, published, binding, etc)
• If you need a class property in your View Model (for some reason) - you need to mark it as ObservableObject/Observed object and assign them into View's object !!!!!!!! inside init() of View. !!!!!!!
• Sometimes is needed to use hacks. But this is really-really-really exclusive situation! In most cases this wrong way! One more time: Please, use structs instead of classes!

Your UI will be refreshed automatically if all of written above was used correctly.

Sample of correct usage:

struct SomeView : View {
    @ObservedObject var model : SomeViewModel
    @ObservedObject var someClassValue: MyClass
    
    init(model: SomeViewModel) {
        self.model = model
    
        //as this is class we must do it observable and assign into view manually
        self.someClassValue = model.someClassValue
    }

    var body: some View {
         //here we can use model.someStructValue directly

         // or we can use local someClassValue taken from VIEW, BUT NOT value from model

    }

}

class SomeViewModel : ObservableObject {
    @Published var someStructValue: Bool
    var someClassValue: MyClass = NewMyClass //myClass : ObservableObject

}

And the answer on topic question.

(hacks solutions - prefer do not use this)

Way 1: declare inside of view:

@State var updater: Bool = false

all you need to update is toogle() it: updater.toogle()

---

Way 2: refresh from ViewModel

Works on SwiftUI 2

public class ViewModelSample : ObservableObject
    func updateView(){
        self.objectWillChange.send()
    }
}

---

Way 3: refresh from ViewModel:

works on SwiftUI 1

import Combine
import SwiftUI

class ViewModelSample: ObservableObject {
    private let objectWillChange = ObservableObjectPublisher()

    func updateView(){
        objectWillChange.send()
    }
}

This is another solution what worked for me, using id() identifier. Basically, we are not really refreshing view. We are replacing the view with a new one.

import SwiftUI

struct ManualUpdatedTextField: View {
    @State var name: String
    
    var body: some View {
        VStack {
            TextField("", text: $name)
            Text("Hello, \(name)!")
        }
    }
}

struct MainView: View {
    
    @State private var name: String = "Tim"
    @State private var theId = 0

    var body: some View {
        
        VStack {
            Button {
                name += " Cook"
                theId += 1
            } label: {
                Text("update Text")
                    .padding()
                    .background(Color.blue)
            }
            
            ManualUpdatedTextField(name: name)
                .id(theId)
        }
    }
}

Setting currentPage, as it is a @State, will reload the whole body.