Question

我正在尝试在SwiftUI中使用ForEach在列表中传递简单的字符串数组。

这是我的代码

import SwiftUI

struct ContentView : View {
var testArry:[String] = ["1", "a", "c"]
var body: some View {
List {
    ForEach(testArry) { obj in
        Text("test")
    }
  }
}
}

#if DEBUG

struct ContentView_Previews : PreviewProvider {
 static var previews: some View {
   ContentView()
 }
}
#endif

错误：无法在当前上下文中推断闭包类型

Answer 1

或者，您可以像这样使用.identified(by: \.self)：

import SwiftUI

struct ContentView : View {

    var testArry:[String] = ["1", "a", "c"]

    var body: some View {
        List {
            ForEach(testArry.identified(by: \.self)) { obj in
                Text("test")
            }
        }
    }
}

Answer 2

This是正确的答案。 ForEach方法签名已在Xcode 11 Beta 5中更改，并且identified(by:)方法已被弃用：

public struct ForEach<Data, ID, Content> where Data : RandomAccessCollection, ID : Hashable

自动完成功能显示为：

ForEach(Data, id: KeyPath<Data.Element, ID>, content: (Data.Element) -> Content)

因此，当使用Xcode 11 Beta 5时，您的代码将是：

import SwiftUI

struct ContentView : View 
{
  var testArry:[String] = ["1", "a", "c"]
  var body: some View 
  {
    List 
    {
        // The updated ForEach method, as of Xcode 11 Beta 5
        ForEach(testArry, id: \.self)
        { obj in
            Text("test")
        }
    }
  }
}

Answer 3

您需要在数组上使用.identified(by: \.self)，以使SwiftUI将值本身用作标识符。因此，您应该使用以下代码来更改代码。

struct ContentView : View {
    var testArry:[String] = ["1", "a", "c"]
    var body: some View {
        List {
            ForEach(testArry.identified(by: \.self)) { obj in
                Text("test")
            }
        }
    }
}

Answer 4

尝试如下所示的符合可识别协议：-

struct ContentView: View {
    var testArry: [TestArray] = [TestArray(value: "1"), TestArray(value: "a"), TestArray(value: "c")]
    var body: some View {
        List {
            ForEach(testArry) { obj in
                Text("\(obj.value)")
            }
        }
    }
}
struct ContentView_Previews : PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}
class TestArray: Identifiable {
    let value: String
    init(value: String) {
        self.value = value
    }
}

无法在SwiftUI的当前上下文中推断闭包类型

4 个答案: