Question

我正在尝试从firstArray中获取金额，然后追加到secondArray。我收到此错误： “无法使用类型为'（[[Number]，@escaping（Double）->（））'的参数列表来调用类型'ForEach <_，_，_>'的初始化程序”“

struct Number: Identifiable {
let id = UUID()
let amount: Double
}

struct ContentView: View {

@State var firstArray = [Number(amount: 10),Number(amount: 30),Number(amount: 50)]
@State var secondArray = [Double]()

var body: some View {
    VStack {
        ForEach(firstArray) { row in
            secondArray.append(row.amount)
        }
    }
}
}

Answer 1

任何标有@State的东西都是真理。如果第二个数组始终依赖于第一个数组，则它不应是状态变量（可以是使用map的计算属性，如下所示）。

如果确定要具有两个@State变量，则应分别对其进行初始化，而不要在视图中对其进行更改。

///MARK: - computed property
struct Number: Identifiable {
    let id = UUID()
    let amount: Double
}
struct ContentView: View {
    @State var firstArray = [Number(amount: 10),Number(amount: 30),Number(amount: 50)]
    var secondArray: [Double] = {
        return firstArray.map { $0.amount }
    }

    var body: some View {
        VStack {
//            ForEach(firstArray) { row in
//                secondArray.append(row.amount)
//            }
        }
    }
}

struct Number: Identifiable {
    let id = UUID()
    let amount: Double
}
struct ContentView: View {
    @State var firstArray = [Number(amount: 10),Number(amount: 30),Number(amount: 50)]
    var secondArray = firstArray.map { $0.amount }

    var body: some View {
        VStack {
//            ForEach(firstArray) { row in
//                secondArray.append(row.amount)
//            }
        }
    }
}

struct Number: Identifiable {
    let id = UUID()
    let amount: Double
}
struct ContentView: View {
    @State var firstArray = [Number(amount: 10),Number(amount: 30),Number(amount: 50)]
    @State var secondArray = firstArray.map { $0.amount }

    var body: some View {
        VStack {
//            ForEach(firstArray) { row in
//                secondArray.append(row.amount)
//            }
        }
    }
}

我强烈建议您使用第一个选项，因为它将始终在第二个数组中包含所有内容的amount。

是否可以从struct数组中获取一项，然后追加到SwiftUI中的其他数组？

1 个答案: