Question

我在struct中有一个带字典的结构，我想访问struct中字典的内容。

这是我的结构：

struct TransactionsObject: Codable {
    let UserInitiatedTransactions: [UserEdTransaction]?
    let UserReceivedTransactions: [UserEdTransaction]?

    enum CodingKeys: String, CodingKey {
        case UserInitiatedTransactions = "UserInitiatedTransactions"
        case UserReceivedTransactions = "UserReceivedTransactions"
    }
}

struct UserEdTransaction: Codable {
    let transactionCode: Int?
    let transactionDate: String?
    let transactionType: String?
    let transactionTime: String?
    let transactionAmount: String?
    let transactionTo: String?
    let transactionFrom: String?

    enum CodingKeys: String, CodingKey {
        case transactionCode = "transactionCode"
        case transactionDate = "transactionDate"
        case transactionType = "transactionType"
        case transactionTime = "transactionTime"
        case transactionAmount = "transactionAmount"
        case transactionTo = "transactionTo"
        case transactionFrom = "transactionFrom"
    }
}

我想访问此 transactionCode 。我试过这个到TransactionsObject.UserInitiatedTransactions.transactionCode，我得到以下错误：

Value of type '[UserEdTransaction]?' has no member 'transactionCode'

Answer 1

首先问题应该是如何在结构中访问数组

仅当结构成员和键与例如 lowerCamelCase 变量名称不匹配时，才使用CodingKeys。

第三，只声明结构的成员是可选的，其关键等价物可能缺失

struct TransactionsObject: Codable {
    let userInitiatedTransactions: [UserEdTransaction]
    let userReceivedTransactions: [UserEdTransaction]

    enum CodingKeys: String, CodingKey {
        case userInitiatedTransactions = "UserInitiatedTransactions"
        case userReceivedTransactions = "UserReceivedTransactions"
    }
}

struct UserEdTransaction: Codable { // no CodingKeys !!
    let transactionCode: Int
    let transactionDate: String
    let transactionType: String
    let transactionTime: String
    let transactionAmount: String
    let transactionTo: String
    let transactionFrom: String
}

发生错误是因为userInitiatedTransactions是一个数组。您需要索引订阅

print(transactionsObject.userInitiatedTransactions[0]) // can crash if the array is empty

或重复循环

for transaction in transactionsObject.userInitiatedTransactions {
    print(transaction.transactionCode)
}

Answer 2

你没有字典。 UserInitiatedTransactions是一个数组。数组没有transactionCode，但是数组的元素有。{/ p>

现在问题变成了，您想要哪个交易的交易代码？

如果你想要第一个，你可以这样做：

someTransactionsObject.UserInitiatedTransactions.first?.transactionCode

如果你想要第四个，

someTransactionsObject.UserInitiatedTransactions[3].transactionCode

如果你想要第n个，

someTransactionsObject.UserInitiatedTransactions[n-1].transactionCode

或者您可以获得一系列交易代码：

someTransactionsObject.UserInitiatedTransactions.map { $0.transactionCode }

Answer 3

您正在访问array作为UserEdTransaction对象，因此您需要从数组中获取对象，然后使用如下所示：

TransactionsObject.UserInitiatedTransactions.first.transactionCode

或

TransactionsObject.UserInitiatedTransactions[0].transactionCode

或

TransactionsObject.UserInitiatedTransactions.forEach { (object) in print(object.transactionCode) }

如何访问结构中的字典

3 个答案: