以编程方式导航到SwiftUI中的新视图

Question

描述性示例：

登录屏幕，用户点击“登录”按钮，执行请求，UI显示等待指示器，然后在成功响应后，我想自动将用户导航到下一个屏幕。

如何在SwiftUI中实现这种自动转换？

Answer 1

成功登录后，可以使用登录视图替换下一个视图。例如：

struct LoginView: View {
    var body: some View {
        ...
    }
}

struct NextView: View {
    var body: some View {
        ...
    }
}

// Your starting view
struct ContentView: View {

    @EnvironmentObject var userAuth: UserAuth 

    var body: some View {
        if !userAuth.isLoggedin {
            LoginView()
        } else {
            NextView()
        }

    }
}

您应该在数据模型中处理登录过程，并使用绑定（例如）@EnvironmentObject传递isLoggedin给视图。

注意：在Xcode中11.0版测试4，以符合协议“BindableObject”的willChange属性已被添加

import Combine

class UserAuth: ObservableObject {

  let didChange = PassthroughSubject<UserAuth,Never>()

  // required to conform to protocol 'ObservableObject' 
  let willChange = PassthroughSubject<UserAuth,Never>()

  func login() {
    // login request... on success:
    self.isLoggedin = true
  }

  var isLoggedin = false {
    didSet {
      didChange.send(self)
    }

    // willSet {
    //       willChange.send(self)
    // }
  }
}

Answer 2

为了将来参考，由于许多用户报告收到错误“函数声明不透明的返回类型”，从@MoRezaFarahani 实现上述代码需要以下语法：

struct ContentView: View {

    @EnvironmentObject var userAuth: UserAuth 

    var body: some View {
        if !userAuth.isLoggedin {
            return AnyView(LoginView())
        } else {
            return AnyView(NextView())
        }

    }
}

这适用于 Xcode 11.4 和 Swift 5

Answer 3

struct LoginView: View {
    
    @State var isActive = false
    @State var attemptingLogin = false
    
    var body: some View {
        ZStack {
            NavigationLink(destination: HomePage(), isActive: $isActive) {
                Button(action: {
                    attlempinglogin = true
                    // Your login function will most likely have a closure in 
                    // which you change the state of isActive to true in order 
                    // to trigger a transition
                    loginFunction() { response in
                        if response == .success {
                            self.isActive = true
                        } else {
                            self.attemptingLogin = false
                        }
                    }
                }) {
                    Text("login")
                }
            }
            
            WaitingIndicator()
                .opacity(attemptingLogin ? 1.0 : 0.0)
        }
    }
}

将导航链接与 $isActive 绑定变量一起使用