如何使用@EnvironmentObject 在 SwiftUI 中自动填充和更新列表？

Question

Like the title says, I'm trying to use an @EnvironmentObject that holds data to populate and update a List automatically in SwiftUI.

For context, I'm building an app that is supposed to show a list of locations. The location data will be shown in multiple places of my app and will be changing during use, so I thought an @EnvironmentObject would be perfect for holding the data. But, I'm having trouble feeding an @EnvironmentObject to populate a List() and having the list update as the @EnvironmentObject changes.

---

Below is the struct I created for the location data I want to display:

struct ListVenue : Identifiable {
    var id = UUID()
    var name: String
    var formatted_address : String?
    var website : String?    
}

Below is my SceneDelegate.swift file, where I create the @EnvironmentObject and the class it references:

import UIKit
import SwiftUI


class venDataArray: ObservableObject {
    var array : [ListVenue] = [ListVenue(name: "test_name")]
}


class SceneDelegate: UIResponder, UIWindowSceneDelegate {

    var window: UIWindow?
    @EnvironmentObject var VDArray: venDataArray

    func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {
        // Use this method to optionally configure and attach the UIWindow `window` to the provided UIWindowScene `scene`.
        // If using a storyboard, the `window` property will automatically be initialized and attached to the scene.
        // This delegate does not imply the connecting scene or session are new (see `application:configurationForConnectingSceneSession` instead).

        // Create the SwiftUI view that provides the window contents.
        let contentView = ContentView().environmentObject(VDArray)

        // Use a UIHostingController as window root view controller.
        if let windowScene = scene as? UIWindowScene {
            let window = UIWindow(windowScene: windowScene)
            window.rootViewController = UIHostingController(rootView: contentView)
            self.window = window
            window.makeKeyAndVisible()
        }
    }

    func sceneDidDisconnect(_ scene: UIScene) {
        // Called as the scene is being released by the system.
        // This occurs shortly after the scene enters the background, or when its session is discarded.
        // Release any resources associated with this scene that can be re-created the next time the scene connects.
        // The scene may re-connect later, as its session was not neccessarily discarded (see `application:didDiscardSceneSessions` instead).
    }

    func sceneDidBecomeActive(_ scene: UIScene) {
        // Called when the scene has moved from an inactive state to an active state.
        // Use this method to restart any tasks that were paused (or not yet started) when the scene was inactive.
    }

    func sceneWillResignActive(_ scene: UIScene) {
        // Called when the scene will move from an active state to an inactive state.
        // This may occur due to temporary interruptions (ex. an incoming phone call).
    }

    func sceneWillEnterForeground(_ scene: UIScene) {
        // Called as the scene transitions from the background to the foreground.
        // Use this method to undo the changes made on entering the background.
    }

    func sceneDidEnterBackground(_ scene: UIScene) {
        // Called as the scene transitions from the foreground to the background.
        // Use this method to save data, release shared resources, and store enough scene-specific state information
        // to restore the scene back to its current state.
    }


}

And, here is the my ContentView.swift file where I want to use the @EnvironmentObject above to populate and update a List() automatically:

import SwiftUI



struct ContentView: View {


    @EnvironmentObject var VDArray: venDataArray


    var body: some View {

    VStack(alignment: .leading) {

        Text("Location List")

    //  This is where im failing at having a list take in an @EnvironmentObject
        List(VDArray) { ListVenue in 
        //  vvv  This is the view I want displayed for each item in the @EnvironmentObject  vvv
            VenueRowTest()
        }
    }
}

Can anyone show me how to alter my code so that I can display and update data in a list using an @EnvironmentObject??

Or is there a better way to implement a dynamic List?

Answer 1

Have a look at the following tutorials:

How to use environmentobject to share data

Apple - handling user inputs

First You need a @Published property wrapper for your code to work.

class VenDataArray: ObservableObject {
@Published var array : [ListVenue] = [ListVenue(name: "test_name")]
}

Than adjust yout Scene delegate

var window: UIWindow?
var vDArray = VenDataArray()

let contentView = ContentView().environmentObject(vDArray)

Note: I have adjusted the variables with lowerCamelCase acc. to the API design guidelines