[英]SwiftUI - View showing Elements conforming to a Protocol and ForEach over them
I want to write a SwiftUI View ListOfMyStruct that operates on an Array of Elements conforming to a given Protocol MyProtocol .我想编写一个 SwiftUI 视图ListOfMyStruct ,它对符合给定协议MyProtocol的元素数组进行操作。
The example works, but of course I need to ForEach over the Elements of the Array (as tried in the commented out lines).该示例有效,但当然我需要对数组的元素进行 ForEach(如在注释掉的行中所尝试的那样)。
Using ForEach, I get: Value of protocol type 'MyProtokoll' cannot conform to 'Hashable';使用 ForEach,我得到:协议类型“MyProtokoll”的值不能符合“Hashable”; only struct/enum/class types can conform to protocols .只有 struct/enum/class 类型可以符合协议。
If I try to let MyProtocol conform to Hashable I get: Protocol 'MyProtokoll' can only be used as a generic constraint because it has Self or associated type requirements .如果我尝试让MyProtocol符合Hashable我得到: Protocol 'MyProtokoll' can only be used as a generic constraint because it has Self or associated type requirements 。
How can I archive this?我该如何存档?
struct PTest: View {
@State var allMyStruct : [MyStruct] =
[ MyStruct(name: "Frank Mueller", myshortName: "fm", a_lot_of_other_sttributes: "bla"),
MyStruct(name: "Tom Smith", myshortName: "ts", a_lot_of_other_sttributes: "bla")
]
var body: some View {
VStack {
Text("Hello, world!")
ListOfMyStruct(elements: allMyStruct)
}
.frame(width: 400, height: 400, alignment: .center)
.padding()
}
}
struct ListOfMyStruct: View {
var elements : [MyProtokoll]
var body: some View {
HStack {
Text("Elements of MyProtocol: ")
Text("\(elements[0].shortName() )")
Text("\(elements[1].shortName() )")
// ForEach(elements, id: \.self) { myProtocol in
// Text("\(myProtocol.shortName())")
// }
}
}
}
//protocol MyProtokoll : Identifiable, Hashable {
protocol MyProtokoll {
var id: String { get }
func shortName() -> String
}
struct MyStruct :MyProtokoll {
var id : String {myshortName}
var name : String
var myshortName :String
var a_lot_of_other_sttributes : String
func shortName() -> String {
myshortName
}
}
It is possible to use iteration by indices.可以通过索引使用迭代。
Here is a fixed part (tested with Xcode 12.4)这是一个固定部分(用 Xcode 12.4 测试)
HStack {
// Text("Elements of MyProtocol: ")
// Text("\(elements[0].shortName() )")
// Text("\(elements[1].shortName() )")
ForEach(elements.indices, id: \.self) { i in
Text("\(elements[i].shortName())")
}
}
also the solution is to specify id
explicitly, like解决方案也是明确指定id
,例如
ForEach(elements, id: \.id) { myProtocol in
Text("\(myProtocol.shortName())")
}
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