使用数组作为属性访问struct时出错

问题描述 投票:0回答:2

我试图使用属性get / set访问结构数组每个TransactionRecord Struct都有位置,每个位置都有一系列事务。每个事务都是TransactionRecord类型

这是我的代码:

struct TransactionRecord {
    var transactionId: String
    var transactionType: String
}

struct TransactionPackage{
    var location: String
    var transactions: [TransactionRecord]
}
var data = TransactionPackage(location: "", transactions: []) {
        didSet {
            if oldValue == nil || data == nil {
                tableView.reloadData()
            }
        }
    }

    var transaction: TransactionPackage {
        get {
            var transactions = [TransactionRecord]()
            if data.transactions.count > 1 {
                for transaction in data.transactions.last ?? [TransactionRecord]  {
                     transactions.append(transaction)
                }
            }
            return TransactionPackage(location: data.location, transactions: transactions)
        }
        set {
           data = [[newValue.location], newValue.transactions]
        }
    }

我收到多个错误:在线:对于data.transactions.last中的事务? [TransactionRecord] {我得到错误:无法将类型'[TransactionRecord] .Type'的值转换为预期的参数类型'TransactionRecord'

在行:data = [[newValue.location],newValue.transactions]我收到错误:无法指定类型'[Any]'的值来键入'TransactionPackage'

我可以得到一些帮助吗?

arrays struct swift4
2个回答
0
投票

第一个错误表示您使用类型[TransactionRecord]作为默认值而不是类型的实例,例如空数组[]

第二个错误说你不能将[Any]赋值为TransactionPackage

我想你想把data映射到transaction作为计算属性

var transaction: TransactionPackage {
    get {
        return TransactionPackage(location: data.location, transactions: data.transactions)
    }
    set {
       data = TransactionPackage(location: newValue.location, transactions: newValue.transactions)
    }
}

或者更简单

var transaction: TransactionPackage {
    get {
        return data
    }
    set {
       data = newValue
    }
}

0
投票

这是更正的代码。

    struct TransactionRecord {
        var transactionId: String
        var transactionType: String
    }

    struct TransactionPackage{
        var location: String
        var transactions = [TransactionRecord]()
    }
    var data = TransactionPackage(location: "", transactions: []) {
        didSet {
                //tableView.reloadData()
        }
    }

    var transaction: TransactionPackage {
        get {
            var trans = [TransactionRecord]()
            if data.transactions.count > 1 {
//Corrections 1,2
                for transaction in data.transactions ?? []  {
                    trans.append(transaction)
                }
            }
            return TransactionPackage(location: data.location, transactions: trans)
        }
        set {
//Corrections 3
            data = TransactionPackage(location: newValue.location, transactions: newValue.transactions)
        }
    }

更正

  1. 在For循环中,您必须传递数组而不是最后一个值。
  2. ??用于提供默认值。
  3. 数据是TransactionPackage,因此您需要将其指定为完整的TransactionPackage。或者你可以这样做。
data.location = newValue.location
data.transactions = newValue.transactions
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