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swift - 如何使用字典对同一键的值求和？

问题描述

我有一本看起来像这样的字典：

(value: 21.0, id: "JdknnhshyrY56AXQcAiLcYtbVlz2") ---> This has a second entry
(value: 18.0, id: "nIvb519nNfMtlVNnsQJ5w4bRbFp2")
(value: 14.0, id: "tlKqcxHdPoemwGqJsyLhERnuQ3Z2")
(value: 5.0,  id: "JdknnhshyrY56AXQcAiLcYtbVlz2")]---> This is the second entry

如果有重复条目，我想将值添加到相同的 id。像这样的东西：

(value: 26.0, id: "JdknnhshyrY56AXQcAiLcYtbVlz2") ---> Value has added and key has become only one
(value: 18.0, id: "nIvb519nNfMtlVNnsQJ5w4bRbFp2")
(value: 14.0, id: "tlKqcxHdPoemwGqJsyLhERnuQ3Z2")]

我已经尝试使用 map 方法，但一直在工作，添加了值，但 id 上的多个条目仍然保持多个条目。

我怎样才能达到结果。

标签： swiftsortingdictionary

解决方案

始终建议将您的Dictionary（具有最终归入[AnyHashable : Any] 类别的异构类型的值）转换为Typed对象。使用类型化的对象，操作或其他计算变得很方便。

在上述陈述的前提下，您将执行以下操作：

let objects = [Object]() // this would be you array with actual data
let reduced = objects.reduce(into: [Object]()) { (accumulator, object) in
    if let index = accumulator.firstIndex(where: { $0.id == object.id }) {
        accumulator[index].value += object.value
    } else {
        accumulator.append(object)
    }
}

在哪里Object：

struct Object {
    var value: Double
    let id: String
}

现在，如果您想知道如何将您的Dictionaryto & fromObject类型转换，请查看完整代码：

let arrayOfDictionary = [["value": 21.0, "id": "JdknnhshyrY56AXQcAiLcYtbVlz2"],
                         ["value": 18.0, "id": "nIvb519nNfMtlVNnsQJ5w4bRbFp2"],
                         ["value": 14.0, "id": "tlKqcxHdPoemwGqJsyLhERnuQ3Z2"],
                         ["value": 5.0,  "id": "JdknnhshyrY56AXQcAiLcYtbVlz2"]]

struct Object: Codable {
    var value: Double
    let id: String
}

do {
    let jsonData = try JSONSerialization.data(withJSONObject: arrayOfDictionary, options: [])
    let objects = try JSONDecoder().decode([Object].self, from: jsonData)

    let reduced = objects.reduce(into: [Object]()) { (accumulator, object) in
        if let index = accumulator.firstIndex(where: { $0.id == object.id }) {
            accumulator[index].value += object.value
        } else {
            accumulator.append(object)
        }
    }

    let encodedObjects = try JSONEncoder().encode(reduced)
    let json = try JSONSerialization.jsonObject(with: encodedObjects, options: [])
    if let reducedArrayOfDictionary = json as? [[String : Any]] {
        print(reducedArrayOfDictionary)
    }
} catch {
    print(error)
}

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