如何根据其中的键值组织字典数组？

Question

我有一个信息数组存储如下：

(
            {
        actual = "<null>";
        code = "AUTO.US";
        date = "2019-12-31";
        difference = "<null>";
        estimate = "-0.12";
        percent = "<null>";
        "report_date" = "2020-03-27";
    },
            {
        actual = "<null>";
        code = "APTX.US";
        date = "2019-12-31";
        difference = "<null>";
        estimate = "-0.5600000000000001";
        percent = "<null>";
        "report_date" = "2020-03-30";
    },
{

        actual = "<null>";
        code = "BLAH.US";
        date = "2019-12-31";
        difference = "<null>";
        estimate = "-0.5600000000000001";
        percent = "<null>";
        "report_date" = "2020-03-30";
    }
);

我想创建一个字典数组，每个report_date 的键包含与该日期匹配的上述字典数组。这就是我想要完成的：

(
        {
        "2020-03-27" =         (
                        {
                actual = "<null>";
                code = "AUTO.US";
                date = "2019-12-31";
                difference = "<null>";
                estimate = "-0.12";
                percent = "<null>";
                "report_date" = "2020-03-27";
            }
        );
    },
        {
        "2020-03-30" =         (
                        {
                actual = "<null>";
                code = "APTX.US";
                date = "2019-12-31";
                difference = "<null>";
                estimate = "-0.5600000000000001";
                percent = "<null>";
                "report_date" = "2020-03-30";
            },
        {

        actual = "<null>";
        code = "BLAH.US";
        date = "2019-12-31";
        difference = "<null>";
        estimate = "-0.5600000000000001";
        percent = "<null>";
        "report_date" = "2020-03-30";
    }
        );
    }
)

为澄清起见，我想得到一个数组，其中包含日期为日期的字典，其对象包含具有与该键匹配的 report_date 的原始字典数组。因此，键下的数组中可能有多个收入字典。

感谢您对此提供的任何帮助！

Answer 1

你不应该在 Swift 中使用 NSDictionary 或 NSArray，除非在极少数情况下。你应该使用 Swift 数组和字典。如果您创建了一个适当的struct 来保存您的数据而不是使用原始字典，这也会有所帮助。如果您的数据来自 JSON，那么您可以使用 Codable 非常简单地转换您的数据。

但是，使用您所拥有的，您需要将 [String:String] 字典数组转换为 [String:String], keyed by a[String]or the rather ugly[String:[[String:String]]] 数组字典`：

为此，只需遍历初始数组，将每个字典添加到 [String:[[String:String]]] 字典：

func createEarningsDictionary(from earnings:[[String:String]] ) -> [String:[[String:String]]] {
    var arrayOfEarningsDicts = [String:[[String:String]]]()

    for earning in earnings {
        if let reportDate = earning["report_date"] {
            arrayOfEarningsDicts[reportDate, default:[[String:String]]()].append(earning)
    }
    return arrayOfEarningsDicts
}

如果您使用 Earnings 结构而不是 [String:String] 字典，您将拥有更易读的内容：

func createEarningsDictionary(from earnings:[Earnings] ) -> [String:[Earnings]] {
    var earningsDict = [String:[Earnings]]()

    for earning in earnings {
        earningsDict[earning.reportDate, default:[Earnings]()].append(earning)
    }
    return earningsDict
}

Answer 2

这个问题有点误导，但是：

原始数据已经是[[String: String]] 类型的数组，而您需要的结果是[[String: [String: String]]] 类型的数组。

按照以下代码到达那里：

// building the original data
var dic1: [String: String] = [:]
dic1["actual"] = "<null>"
dic1["code"] = "AUTO.US"
dic1["date"] = "2019-12-31"
dic1["difference"] = "<null>"
dic1["estimate"] = "-0.12"
dic1["percent"] = "<null>"
dic1["report_date"] = "2020-03-27"

var dic2: [String: String] = [:]
dic2["actual"] = "<null>"
dic2["code"] = "APTX.US"
dic2["date"] = "2019-12-31"
dic2["difference"] = "<null>"
dic2["estimate"] = "-0.5600000000000001"
dic2["percent"] = "<null>"
dic2["report_date"] = "2020-03-30"

// the array of the original data
let array = [dic1, dic2]

// the interesting function
func sortThemOut() {
    var finalArray: [[String: [String: String]]] = []
    for dic in array {
        // get the `report_date` value from the original dictionary
        let reportDate = dic["report_date"] ?? "there was no value for the `report_date`"
        // create the new item that should be appended in the new array
        var newDic: [String: [String: String]] = [:]
        // set the key to the `reportDate`, and the value of that key to the original dictionary
        newDic[reportDate] = dic
        
        // append the new dictionary into the final array
        finalArray.append(newDic)
    }
    print(finalArray)
}

我仍然强烈建议您将其更改为将原始数据转换为 [String: [String: String]] 类型的字典，我相信这是您真正想要得到的：

// the array of the original data
let array = [dic1, dic2]

func sortThemOut() {
    var finalDictionary: [String: [String: String]] = [:]
    for dic in array {
        // get the `report_date` value from the original dictionary
        let reportDate = dic["report_date"] ?? "there was no value for the `report_date`"
        // set the key to the `reportDate`, and the value of that key to the original dictionary
        finalDictionary[reportDate] = dic
    }
    print(finalDictionary)
}

你可以这样使用：

    // key will represent the `report_date`, and the value will contain the rest of the object
    for (key, value) in finalDictionary {
        print("key: " + key)
        print("value: \(value)")
        
        // OUTPUT:
        
        // key: 2020-03-27
        // value: ["report_date": "2020-03-27", "estimate": "-0.12", "code": "AUTO.US", "difference": "<null>", "date": "2019-12-31", "actual": "<null>", "percent": "<null>"]
        
        // key: 2020-03-30
        // value: ["report_date": "2020-03-30", "estimate": "-0.5600000000000001", "date": "2019-12-31", "difference": "<null>", "percent": "<null>", "actual": "<null>", "code": "APTX.US"]
    }
    
    print(finalDictionary["2020-03-27"])
    // ["report_date": "2020-03-27", "estimate": "-0.12", "code": "AUTO.US", "difference": "<null>", "date": "2019-12-31", "actual": "<null>", "percent": "<null>"]

更新

根据以下 cmets 中的说明，生成的对象将是 `[String: [[String: String]]]' 类型的字典，因此函数为：

func sortThemOut() {
    var finalDictionary: [String: [[String: String]]] = [:]
    for dic in array {
        // get the `report_date` value from the original dictionary
        let reportDate = dic["report_date"] ?? "there was no value for the `report_date`"
        // creating an array that will hold the original objects
        // try to get the array that was previously inserted (if a previous object with same report_date was inserted before, or assign an new empty array
        var objects = finalDictionary[reportDate] ?? []
        
        // append the object into the array
        objects.append(dic)
        
        // set the key to the `reportDate`, and the value of that key to the array of original objects
        finalDictionary[reportDate] = objects
    }
}