arrays - 向后浏览词典以查找上次更新值的时间

Question

我有一个字典数组，其中有两个感兴趣的键对。一对 key 是日期，另一对是“investpercent”，其值经常变化。我想查找 investpercent 的最后更新日期。所以，请考虑:

var importedRecords = [
["low": "1.0", "date": "2018-04-25", "objective": "2.0", "savings": "2.0", "high": "2.0", "expenses": "1.0", "investpercent": "3.0"], 
["low": "1.0", "date": "2018-05-25", "objective": "2.0", "savings": "2.0", "high": "2.0", "expenses": "1.0", "investpercent": "3.0"], 
["low": "1.0", "date": "2018-06-25", "objective": "2.0", "savings": "2.0", "high": "2.0", "expenses": "1.0", "investpercent": "4.0"], 
["low": "1.0", "date": "2018-07-25", "objective": "2.0", "savings": "2.0", "high": "2.0", "expenses": "1.0", "investpercent": "4.0"], 
["low": "1.0", "date": "2018-08-25", "objective": "2.0", "savings": "2.0", "high": "2.0", "expenses": "1.0", "investpercent": "5.0"], 
["low": "2", "date": "2018-09-26", "objective": "2.0", "savings": "2.0", "high": "4", "expenses": "1.0", "investpercent": "5.0"]
]

现在，请注意 investpercent 最后一次更改是在“2018-08-25”，我感兴趣的值是“5.0”。我的想法是这样的:

var lastentry = importedRecords.suffix(1)
var lastdate: String = ""
for record in importedRecords {
    if record["investpercent"] == lastentry["investpercent"] {
        lastdate = record["date"]
    }

}

但我无法尝试将该数组切片转换为合适的字典。

• 如何浏览此数组以检测上次更新 investpercent 的日期？

Answer 1

这应该可以解决问题，它使用 zip :

let reversedRecords = importedRecords.reversed()
let zipped = zip(reversedRecords.dropFirst(), reversedRecords)

if let twoDictionaries = zipped.first(where: {$0["investpercent"] != $1["investpercent"]}),
    let date = twoDictionaries.1["date"] {
    print(date)
}

它打印 2018-08-25