Question

我有一堂课，看起来像这样：

public class TransactionResults: Identifiable {
    public typealias CustomClassValue = Transaction
    public typealias CustomClassIndex = Array<CustomClassValue>.Index

    public let id = UUID()
    private let transactions = sampleTransactions
}

extension TransactionResults: RandomAccessCollection {
    public var startIndex: CustomClassIndex { return transactions.startIndex }
    public var endIndex: CustomClassIndex { return transactions.endIndex }

    public subscript(index: CustomClassIndex) -> CustomClassValue? {
        get { if index >= 0 && index < transactions.count {
            return transactions[index]
            } else {
            return nil
            }
        }
    }
}

当我尝试将其与ForEach一起使用时，出现错误：Cannot convert value of type 'TransactionResults' to expected argument type 'Range<Int>'

struct TransactionListView: View {
    @State private var transactions = TransactionResults()

    var body: some View {
        NavigationView {
            List() {
                ForEach(transactions) { transaction in
                    EmptyView()
                }
            }
        }
    }
}

要使其正常运行，我需要在TransactionResults类中进行哪些更改？

Answer 1

如果您正确声明了Transaction类（顺便说一下，它可能会与SwiftUI Transaction类型冲突，所以我建议重命名您的类型），那么就需要全部（至少与Xcode 11.4）将使用其他ForEach构造函数：

ForEach(transactions, id: \.self) { transaction in
    EmptyView()
}

更新：这是一个用于测试代码快照的事务类（正如我提到的，我将其重命名以避免与内置类型冲突）

class ATransaction: Equatable, Identifiable, Hashable {
    static func == (lhs: ATransaction, rhs: ATransaction) -> Bool {
        lhs.id == rhs.id
    }

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

    let id = UUID()
}

如何在ForEach列表中使用RandomAccessCollection？

1 个答案: