如何在Swift 4中对数组日期进行排序

Question

我有这样的日期数组：-

  var dateArray = ["2016-04-20", "2016-04-22", "2016-04-25", "2016-04-30"]

我想找出两者之间的天数差异。 我做了一些研究，我只用两个约会就可以做到这一点，这是我发现两个约会之间的区别的方法

let dateFormatter = DateFormatter()
let isoDate = "2016-04-20"
let calendar = NSCalendar.current
let currentDate = Date()

在我的viewDidLoad方法中，我做到了

    override func viewDidLoad() {
    super.viewDidLoad()



//  let components = calendar.dateComponents([.day], from: )
    dateFormatter.dateFormat = "yyyy-MM-dd"
    dateFormatter.locale = Locale(identifier: "en_US_POSIX") //en_US_POSIX
    let formatedStartDate = dateFormatter.date(from: isoDate)
    let date = dateArray.compactMap { dateFormatter.date(from: $0) } // for date array
    print(date)
    let components = Set<Calendar.Component>([.day])
    let differenceOfDate = Calendar.current.dateComponents(components, from: formatedStartDate!, to: currentDate )

    print (differenceOfDate)
    apiData()
}

如您在代码中看到的，我创建了一个常量let isoDate =“ 2016-04-20”并更改为formattedStartDate，并找到此日期与当前日期之间的差异，然后它起作用了。 但是，如果我有自己的日期数组，又怎么能找到自己的日期数组的差异并将其按升序或降序排序呢？ 请帮忙？

Answer 1

• 创建日期格式

   let dateFormatter = DateFormatter() dateFormatter.dateFormat = "yyyy-MM-dd" dateFormatter.locale = Locale(identifier: "en_US_POSIX") //en_US_POSIX 

• 将日期字符串数组映射到Date实例

   let dateStringArray = ["2016-04-20", "2016-04-22", "2016-04-25", "2016-04-30"] let dateArray = dateStringArray.map {dateFormatter.date(from: $0)!} // add .sorted() if the array is unordered. 

• 循环获得相邻项目之间的差异

   var differences = [Int]() for i in 0..<dateArray.count - 1 { let dayComponent = Calendar.current.dateComponents([.day], from: dateArray[i], to: dateArray[i+1]) differences.append(dayComponent.day!) } print(differences) 

Answer 2

我不确定您是否只想比较相邻的日期或比较每个日期。 在第一种情况下，请使用vadian的解决方案。 在其他情况下，您可以执行以下操作：

let dateStrings = ["2016-04-20", "2016-04-22", "2016-04-25", "2016-04-30"]

let dateFormatter = DateFormatter()
dateFormatter.dateFormat = "yyyy-MM-dd"
dateFormatter.locale = Locale(identifier: "en_US_POSIX")

let dates = dateStrings.compactMap { dateFormatter.date(from: $0) }

let calendar = Calendar.current

var differences: [Int] = []
for i in 0..<dates.count {
    for j in i + 1..<dates.count {
        if let difference = calendar.dateComponents([.day], from: dates[i], to: dates[j]).day {
            differences.append(difference)
        }
    }
}

let descendingDifferences = differences.sorted(by: >)
print(descendingDifferences) // results in [10, 8, 5, 5, 3, 2]