Swap between views on button press - SwiftUI - ios

Question

I am a beginner to swift, and i want to swap between 2 views.
Here is my current code.
I have tried to look at other stackoverflow questions but I dont understand what a viewcontroller or anything is, so if you do answer please explain what it does.
All i want to do is swap from ContentView to MessageView when the sign up button is pressed, but I don't know how to approach this at all.
import SwiftUI
struct ContentView: View {
#State private var username: String = ""
#State private var password: String = ""
var body: some View {
VStack {
Text("Create an account.")
TextField("Username", text: $username)
.textFieldStyle(RoundedBorderTextFieldStyle())
.frame(width: 250, height: /*#START_MENU_TOKEN#*/100/*#END_MENU_TOKEN#*/)
SecureField("Password", text: $password)
.textFieldStyle(RoundedBorderTextFieldStyle())
.frame(width: 250, height: /*#START_MENU_TOKEN#*/100/*#END_MENU_TOKEN#*/)
let button = Button("Sign Up!") {
if(username == "" || password == "") {
print("no suername or password")
} else {
print("user", username)
print("password", password)
}
}
button.cornerRadius(5.0)
}
}
}
struct MessageView: View {
var body: some View {
NavigationView {
List {
Text("FortniteGamer123")
Text("FortniteEpicKid")
Text("KidIsGoodAtFortnite")
}
}.navigationTitle("Fortnite Gamers")
}
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ContentView()
}
}
If anyone could at least give me some help on view controllers and how to use them that would be great.

Answer 1

You're using SwiftUI, which doesn't really have a concept of view controllers (or at least UIViewController), which are more part of UIKit.
SwiftUI, rather, is made up of sets of composable views. You already have a couple that you've defined (like ContentView and MessageView) and are using a bunch of built-in SwiftUI views (like TextField, Text, Button, etc).
To swap between views, you can use an if statement that is dependent on a #State variable.
I refactored things a bit so that LoginView and MessageView are shown by a parent view (ContentView) depending on the state of loggedIn. This is passed via a Binding to LoginView so that when the button is pressed, the value can get passed back up to the parent.
struct ContentView: View { //parent view
#State var loggedIn = false //state variable
var body: some View {
if loggedIn { //'if' condition
MessageView()
} else {
LoginView(loggedIn: $loggedIn) //passing loggedIn with the $ sign makes it a two-way binding where the child view can now have access to and change the variable
}
}
}
struct LoginView : View {
#Binding var loggedIn : Bool //this is how loggedIn gets passed in
#State private var username: String = ""
#State private var password: String = ""
var body: some View {
VStack {
Text("Create an account.")
TextField("Username", text: $username)
.textFieldStyle(RoundedBorderTextFieldStyle())
.frame(width: 250, height: 100)
SecureField("Password", text: $password)
.textFieldStyle(RoundedBorderTextFieldStyle())
.frame(width: 250, height: 100)
Button(action: {
if(username == "" || password == "") {
print("no suername or password")
} else {
print("user", username)
print("password", password)
loggedIn = true //set the binding to true, which will effect the parent view
}
}) {
Text("Sign Up!")
}
.padding()
.overlay(RoundedRectangle(cornerRadius: 5.0).stroke(Color.accentColor)) //using this to round the corners
}
}
}
Technically, you could've also approached this by using NavigationView and NavigationLink, but that would've resulted in a situation where the user could've tapped the back button to go back to the login screen, which isn't really something you see in iOS, so I took your title literally about swapping between the two views.
I made a couple very minor edits to your other code. For example, had a let Button = in the middle of your view hierarchy that I've adjusted -- normally in SwiftUI you won't be defining variables that capture the views -- instead, you'll just be defining them in the hierarchy.

Answer 2

In Swift we have two main framework to build iOS applications: UIKit and SwiftUI. The first one is imperative and the second one - declarative. In UIKit we are using controllers and views classes to create UI and in SwiftUI we are using View structures to declare how we want user interface to show up. Basically SwiftUI in this case is similar to React / React Native and Flutter. In you example you are using SwiftUI, so you need to declare state variable and show the view based on this variable value, for example using .sheet(isPresented: <your state var>) or if statement. Also you could use NavigationView and Navigation Link.