Question

我想使用NSPredicate比较每个对象的日期。如果Object具有相同的dateCreated它将返回一个具有相同日期的对象数组。

在下面的字典数组中，0索引与另一个索引的日期不同，我怎样才能获得这样的数据。

例如：

{
      "Data": [
    {
      "id": "c9967156ad8945fba8cc482cd8aad900",
      "description": "Hi",
      "dateCreated": "2018-03-20T06:15:11.000+0000",

    },
    {
      "id": "343e70818044457b884f7ad1907803fa",
      "description": "The only ",
      "dateCreated": "2018-03-16T17:22:50.000+0000",

    },
    {
      "id": "dd542edfaa364e40ae0ef0562b6831be",
      "description": "The new ",
      "dateCreated": "2018-03-16T17:10:36.000+0000",

    },
    {
      "id": "090f43c83e5b42039f70b133d031e715",
      "description": "The new version ",
      "dateCreated": "2018-03-16T17:08:07.000+0000",

    },
    {
      "id": "b2ddb8fa990843a28f0670d2b88e3d01",
      "description": "Add to the test",
      "dateCreated": "2018-03-16T17:08:07.000+0000",

    }
     ]
    }

＃EDIT1 ：我正在将dateCreated String对象转换为Date，然后我将NSPredicate用于所需数据。目前，我正在尝试使用NSPredicate

＃EDIT2 目前，我没有使用NSPredicate。我正在迭代数组的每个元素并比较它的日期

  if let dateCur = dateCreated.dateFromISO8601 {
     if let datePrev = dateCreatedPrev.dateFromISO8601 {
      let curLocal = ISO8601.getStringDate(dateCur).   // dd/MM/yyyy
      let prevLocal = ISO8601.getStringDate(datePrev). // dd/MM/yyyy
      if (curLocal.compare(prevLocal) != .orderedSame {
           //diffrent
      }else {
          //same
      }
     }
  }

我正在使用扩展来实现它

extension Date {

func getFormatter() -> DateFormatter {
    let formatter = DateFormatter()
    formatter.calendar = Calendar(identifier: .gregorian)
    formatter.locale = Locale(identifier: "en_US_POSIX")
    formatter.timeZone = TimeZone(secondsFromGMT: 0)
    formatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ss.SSSXXXXX"
    return formatter
}

var iso8601: String {
    return Formatter.iso8601.string(from: self)
}

extension String {
  var dateFromISO8601: Date? {
     return Formatter.iso8601.date(from: self)   // "Mar 22, 2017,    10:22 AM"
  }
}

你能帮我吗？

Answer 1

首先，不需要在Swift中使用NSPredicate（除了需要NSPredicate的API）。
原生filter方法更合适。

我建议解码JSON

let jsonString = """
{
    "Data": [
        {"id": "c9967156ad8945fba8cc482cd8aad900", "description": "Hi", "dateCreated": "2018-03-20T06:15:11.000+0000"},
        {"id": "343e70818044457b884f7ad1907803fa", "description": "The only ", "dateCreated": "2018-03-16T17:22:50.000+0000"},
        {"id": "dd542edfaa364e40ae0ef0562b6831be", "description": "The new ", "dateCreated": "2018-03-16T17:10:36.000+0000"},
        {"id": "090f43c83e5b42039f70b133d031e715", "description": "The new version ", "dateCreated": "2018-03-16T17:08:07.000+0000"},
        {"id": "b2ddb8fa990843a28f0670d2b88e3d01", "description": "Add to the test", "dateCreated": "2018-03-16T17:08:07.000+0000"}
    ]
}
"""

进入自定义结构

struct Root : Decodable {
    private enum CodingKeys : String, CodingKey { case items = "Data" }
    let items : [Item]
}

struct Item : Decodable {
    let id, description : String
    let dateCreated : Date
}

解码器使用自定义日期格式化程序正确解码ISO8601日期

let data = Data(jsonString.utf8)
let decoder = JSONDecoder()
let dateFormatter = DateFormatter()
dateFormatter.locale = Locale(identifier: "en_US_POSIX")
dateFormatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ss.SZ"
decoder.dateDecodingStrategy = .formatted(dateFormatter)

do { 
    let result = try decoder.decode(Root.self, from: data)

数组位于result.items。现在，您可以按特定日期filter数组。在此示例中，使用DateComponents硬编码创建参考日期。

    let components = DateComponents(timeZone: TimeZone(secondsFromGMT: 0), year:2018, month:03, day:16, hour:17, minute:8, second:7)
    let date = Calendar.current.date(from: components)!
    let filteredItems = result.items.filter { $0.dateCreated == date }
    print(filteredItems)
} catch { print(error) }

如果要查找数组中给定日期的所有匹配记录，请使用循环

for item in result.items {
    let filteredItems = result.items.filter { $0.dateCreated == item.dateCreated }
    if filteredItems.count > 1 { print(filteredItems) }
}

Answer 2

您可以查看 Swift 4 中引入的Dictionary初始值设定项init(grouping:by:)。

你应该拥有你的对象数组。然后，您可以将[String:Object]分组为key Date yyyy-MM-dd String格式为dateCreated。

先决条件：您的Date媒体资源应为let groupedObjectBySameDate = Dictionary(grouping: objects) { (object) -> String in let formatter = DateFormatter() formatter.dateFormat = "yyyy-MM-dd" return formatter.string(from: object.dateCreated) }格式。

var dateFormatter: DateFormatter {
    let formatter = DateFormatter()
    formatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ss.SZ"
    formatter.locale = Locale(identifier: "en_US_POSIX")
    return formatter
}
let stringDates = ["2018-03-20T06:15:11.000+0000", "2018-03-16T17:22:50.000+0000", "2018-03-16T17:10:36.000+0000", "2018-03-16T17:08:07.000+0000", "2018-03-16T17:08:07.000+0000"]
let dates = stringDates.map { (each) -> Date in
    return dateFormatter.date(from: each) ?? Date(timeIntervalSinceReferenceDate: 0)
}

let groupedObjectBySameDate = Dictionary(grouping: dates) { (date) -> String in
    let formatter = DateFormatter()
    formatter.dateFormat = "yyyy-MM-dd"
    return formatter.string(from: date)
}
print(groupedObjectBySameDate)

// This will produce:
// [
//     "2018-03-20": [2018-03-20 06:15:11 +0000], 
//     "2018-03-16": [2018-03-16 17:22:50 +0000, 2018-03-16 17:10:36 +0000, 2018-03-16 17:08:07 +0000, 2018-03-16 17:08:07 +0000]
// ]

一个例子：

由于我不知道您的数据结构，我提供了一个简单的示例，可以帮助您了解正在发生的事情。

/qwertyae

如何使用NSPredicate比较对象数组中的两个日期字符串？

2 个答案:

一个例子：