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swift - Swift - 在字典中按天分组数据

问题描述

这是字典：

[1549424985: ["amount": "10.0", "symbol": "XRP"], 1546531017: ["amount": "1.0", "symbol": "ETH"], 1549424153: ["amount": "50.0", "symbol": "EOS"], 1546531031: ["amount": "200.0", "symbol": "XRP"]]

typealias CryptoTuple = (symbol: String, amount: Double)
var cryptosPerDay = [String: [CryptoTuple]]()
var prev = ""
groupedData.keys.sorted(by: <).forEach( { key in
    let date = parseToDateString(key)
    if let buy = groupedData[key], let symbol = buy["symbol"], let amountStr = buy["amount"], let amount = Double(amountStr) {
        if prev != date {
            cryptosPerDay[date] = [(symbol, amount)]
            if let old = cryptosPerDay[prev] {
                cryptosPerDay[date]?.append(contentsOf: old)
            }
            prev = date
        } else {
            cryptosPerDay[date]?.append((symbol, amount))
        }
    }
})

这是我上一个问题的答案提供的代码：Calculating doubles by dates with format timeIntervalSince1970 from 2 different dictionaries

但是这段代码返回我重复的值 print(cryptosPerDay) ["2019-02-06": [(symbol: "EOS", amount: 50.0), (symbol: "ETH", amount: 1.0), (symbol: "XRP", amount: 200.0), (symbol: "XRP", amount: 10.0)], "2019-01-03": [(symbol: "ETH", amount: 1.0), (symbol: "XRP", amount: 200.0)]]

如何解决？

标签： swiftdictionarygrouping

解决方案

目前尚不清楚目标是什么，但这里有一种方法可以做我认为你正在尝试做的事情。注意使用结构而不是元组：

let d = [ // your data
    1549424985: ["amount": "10.0", "symbol": "XRP"],
    1546531017: ["amount": "1.0", "symbol": "ETH"],
    1549424153: ["amount": "50.0", "symbol": "EOS"],
    1546531031: ["amount": "200.0", "symbol": "XRP"]
]
struct Trade {
    let amount:Double
    let symbol:String
}
var result = [String:[Trade]]()
for key in d.keys {
    let date = Date(timeIntervalSince1970: Double(key))
    let f = DateFormatter()
    f.dateFormat = "yyyy-MM-dd"
    let dayString = f.string(from: date)
    let val = d[key] as! [String:String]
    let trade = Trade(
        amount: Double(val["amount"]!)!,
        symbol: val["symbol"]!
    )
    result[dayString, default:[]].append(trade)
}

之后，result就是：

["2019-02-06": [Trade(amount: 10.0, symbol: "XRP"), Trade(amount: 50.0, symbol: "EOS")], 
 "2019-01-04": [Trade(amount: 1.0, symbol: "ETH"), Trade(amount: 200.0, symbol: "XRP")]]

...这似乎是“正确”的答案。就个人而言，我认为以这种方式使用日期字符串很愚蠢。最好使用实际日期。在这种情况下，最后一部分可以重写为：

var result = [Date:[Trade]]()
for key in d.keys {
    let date = Date(timeIntervalSince1970: Double(key))
    let day = Calendar(identifier: .gregorian).startOfDay(for: date)
    let val = d[key] as! [String:String]
    let trade = Trade(
        amount: Double(val["amount"]!)!,
        symbol: val["symbol"]!
    )
    result[day, default:[]].append(trade)
}

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