Swiftui How to Invoke the Function and Change View from Other Page

How can I switch the View directly with a function call in SwiftUI?

Since you already have a Bool all you need is a conditional.

If you want it in the Navigation Stack (with a Back button) use the NavigationLink constructor with isActive and use your Bool to make the View active.

import SwiftUI

struct SwitchScreen: View {
    @State var animate = false
    @State var endSplash = false
    var body: some View {
        NavigationView{
            switch endSplash{
            case false:
                ZStack{
                    
                    Color.blue
                    
                    Image(systemName: "checkmark").resizable().renderingMode(.original).aspectRatio(contentMode: animate ? .fill : .fit)
                        .frame(width: animate ? nil : 85, height: animate ? nil: 85)
                        .colorInvert().scaleEffect(animate ? 3 : 1).frame(width: UIScreen.main.bounds.width)
                    
                    
                }.ignoresSafeArea(.all, edges: .all).onAppear(perform: {
                    animateSplash()
                }).opacity(endSplash ? 0:1)
            case true:
                Text("Done")
            }
        }
    }
    func animateSplash(){
        DispatchQueue.main.asyncAfter(deadline: .now() + 0.5){
            withAnimation(Animation.easeOut(duration: 0.45)){
                animate.toggle()
            }
            withAnimation(Animation.linear(duration: 0.35)){
                endSplash.toggle()
                //Switch to another View here I guess ?
            }
        }
    }
}
struct SwitchScreen_Previews: PreviewProvider {
    static var previews: some View {
        SwitchScreen()
    }
}

How to go to another page from a sheet view in SwiftUI?

NavigationLink should be in same view hierarchy of NavigationView to work, but .sheet introduces another different view hierarchy, so the solution would be to leave (hidden) navigation link in previous view, but activate it programmatically from view in sheet.

Here is a demo (tested with Xcode 12 / iOS 14)

struct FirstView: View {
    @State fileprivate var isShowingSheet: Bool = false
    @State private var showThirdView = false

    var body: some View {
        Button(action: {
            isShowingSheet = true
        }) {
            Text("Show the sheet")
        }
        .sheet(isPresented: $isShowingSheet, content: {
            SecondView(showNext: $showThirdView)
        })
        .background(
              NavigationLink(destination: ThirdView(), isActive: $showThirdView) {
                    EmptyView()
              }
        )
    }
}

struct SecondView: View {
    @Environment(\.presentationMode) var presentationMode
    @Binding var showNext: Bool

    var body: some View {
        Button("Show the third view.") {
            self.presentationMode.wrappedValue.dismiss()
            DispatchQueue.main.async {
                self.showNext = true
            }
        }
    }
}

SwiftUI Change Observed Object From Another View

It is changing the value. The problem is you are instantiating an instance of GlobalValue locally in your struct. It has no life outside of the struct. I you want to use an Observable Object as a global store like that, you need to create it once and use that instance.

The easiest way to do this is to add
static let shared = GlobalValue() in your class, and in your struct use globalValue = GlobalValue.shared which essentially gives you a singleton. You will have one instance that all the views can read and write to.

Go to a new view using SwiftUI

The key is to use a NavigationView and a NavigationLink:

import SwiftUI

struct ContentView : View {
    var body: some View {
        NavigationView {
            VStack {
                Text("Hello World")
                NavigationLink(destination: DetailView()) {
                    Text("Do Something")
                }
            }
        }
    }
}

How can I execute some function when a Link is clicked in SwiftUI?

you could also try this using a button as @​aheze suggested:

struct ContentView: View {
    @Environment(\.openURL) var openURL
    
    var body: some View {
        Button(action: openSesame) {
            Text("open url")
        }
    }
    
    func openSesame() {
        // do something here
        print("---> about to open duckduckgo ")
        openURL(URL(string: "https://duckduckgo.com/")!)
        // or/and do something here
        print("---> after openning duckduckgo ")
    }
}

SwiftUI send action from a page to the PageViewController

OK, I figured it out. Not intuitive at first, I have to say. Coming from traditional event based programming, it's quite a different way of thinking

I used a @State variable in the main instance of the view.

I used @Binding variables to deal with the state both upstream (ViewControllers, Controls) and downstream (subviews). So, for example, I used a variable to tell the dataSource of the UIPageViewController if or not to return a view controller before/after the current one.

For the dismissing the modally presented controller I used

@Environment(\.presentationMode) var presentationMode

...

func dismiss() {
  self.presentationMode.wrapptedValue.dismiss()
}

Similarly,

...
@Binding var currentPage: int
...

Button(action: next) { Text("Next Page") }
...

...
func next() {
    currentPage += 1
}

There were a few caveats in deciding how to nest the views and what variables to pick for the bindings, but it is clear to me now. The biggest problem was ultimately where the "source of truth" should be anchored. It turned out, right in the "middle", i.e. below the controller and above the particular views.

Hope this is useful for others looking for something similar.

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