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具有@State属性的ForEach

swiftui foreach swift

Hans · 技术社区 · 6 年前

我有一个 @State 属性(在示例中 @State var parent: Parent ),其中包含一个数组属性,我想在 ForEach

ForEach(parent.children, id: \.self) { child in
    ChildView(child: child)
}

虽然我相信 $ 去召唤 correctly pass it to the child view . 但是我得到一个错误 Unable to infer complex closure return type; add explicit type to disambiguate .

解决这个问题的正确方法是什么?为什么这个代码不正确?

最小复制代码

import UIKit
import SwiftUI

func setup() -> Parent {
    let child = Child(name: "foo")
    let parent = Parent(name: "bar")
    parent.children = [child]
    return parent
}

class Parent {
    var name: String
    var children: [Child] = []

    init(name: String) {
        self.name = name
    }
}

class Child: Hashable {
    static func == (lhs: Child, rhs: Child) -> Bool {
        lhs.name == rhs.name
    }

    func hash(into hasher: inout Hasher) {
        hasher.combine(self.name)
    }

    var name: String

    init(name: String) {
        self.name = name
    }
}

class SceneDelegate: UIResponder, UIWindowSceneDelegate {
    var window: UIWindow?

    func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {
        let parent = setup()
        let parentView = ParentView(parent: parent)

        if let windowScene = scene as? UIWindowScene {
            let window = UIWindow(windowScene: windowScene)
            window.rootViewController = UIHostingController(rootView: parentView)
            self.window = window
            window.makeKeyAndVisible()
        }
    }
}

struct ChildView: View {
    @State var child: Child

    var body: some View {
        VStack {
            Text("Child â\(child.name)â")
        }
    }
}

struct ParentView: View {
    @State var parent: Parent

    var body: some View {
        VStack {
            Text("Parent â\(parent.name)â")
            // ForEach($parent.children, id: \.self) { child in
            // Yields error:
            // Unable to infer complex closure return type; add explicit type to disambiguate
            ForEach(parent.children, id: \.self) { child in
                ChildView(child: child)
            }
        }
    }
}

struct ParentView_Previews: PreviewProvider {
    static var previews: some View {
        let parent = setup()
        return ParentView(parent: parent)
    }
}

0 回复 | 直到 6 年前

mkowal87 6 年前

我不知道你为什么需要这里的美元符号,但我会改变代码如下

class Parent: ObservableObject {
    var name: String
    @Published
    var children: [Child] = []

    init(name: String) {
        self.name = name
    }
}

class Child: Hashable {
    static func == (lhs: Child, rhs: Child) -> Bool {
        lhs.name == rhs.name
    }

    func hash(into hasher: inout Hasher) {
        hasher.combine(self.name)
    }

    var name: String

    init(name: String) {
        self.name = name
    }
}

struct ChildView: View {
    @State var child: Child

    var body: some View {
        VStack {
            Text("Child â\(child.name)â")
        }
    }
}

struct ParentView: View {
    @ObservedObject
    var parent: Parent

    var body: some View {
        VStack {
            Text("Parent â\(parent.name)â")
            // ForEach($parent.children, id: \.self) { child in
            // Yields error:
            // Unable to infer complex closure return type; add explicit type to disambiguate
            ForEach(parent.children, id: \.self) { child in
                ChildView(child: child)
            }
        }
    }
}