Swift：按天比較日期

Question

我嘗試比較兩天而忽略時間。 所以我用

calendar.compare(date1, to: date2, toGranularity: .day)

但是當將字符串日期轉換為 Date 類型時，它會轉換為 UTC。 所以它將從 1.1.2016 0:05 到 31.12.2015 11:05 pm“移動”。 在按日比較時，這僅包括剩余的小時。 在轉換之前是 24 小時。 有什么想法可以毫不費力地處理這個問題嗎？

另外： 代碼：

var dateFormatter = DateFormatter()
dateFormatter.dateFormat = "dd-MM-yyyy hh:mm"
var date1 : Date = dateFormatter.date(from:  "01-01-2016 00:05")!
var date2 = dateFormatter.date(from:  "01-01-2016 03:30")

if let dateFromString = dateFormatter.date(from:  "01-01-2016 00:05") {
    print(dateFromString)
    dateFormatter.timeZone = TimeZone(secondsFromGMT: 0)
    let stringFromDate = dateFormatter.string(from: dateFromString)
}


Calendar.current.compare(date1, to: date2!, toGranularity: .day) == .orderedSame

Answer 1

詳情

• Xcode 11.5 (11E608c)，Swift 5.1

想法

基於使用dateComponents(_:from:to:)函數

解決方案

import Foundation

extension Date {

    func fullDistance(from date: Date, resultIn component: Calendar.Component, calendar: Calendar = .current) -> Int? {
        calendar.dateComponents([component], from: self, to: date).value(for: component)
    }

    func distance(from date: Date, only component: Calendar.Component, calendar: Calendar = .current) -> Int {
        let days1 = calendar.component(component, from: self)
        let days2 = calendar.component(component, from: date)
        return days1 - days2
    }

    func hasSame(_ component: Calendar.Component, as date: Date) -> Bool {
        distance(from: date, only: component) == 0
    }
}

完整樣本

不要忘記把解決方案代碼放在這里（看上面）

var dateFormatter = DateFormatter()
dateFormatter.dateFormat = "dd-MM-yyyy hh:mm:ss"
//dateFormatter.timeZone = TimeZone(secondsFromGMT: 0)

let smallerDate = dateFormatter.date(from: "01-01-2012 00:05:01")!
let biggerDate  = dateFormatter.date(from: "03-12-2019 09:30:01")!

print(smallerDate.fullDistance(from: biggerDate, resultIn: .day))       // Optional(2893)
print(biggerDate.fullDistance(from: smallerDate, resultIn: .day))       // Optional(-2893)
print(smallerDate.fullDistance(from: biggerDate, resultIn: .year))      // Optional(7)
print(biggerDate.fullDistance(from: smallerDate, resultIn: .year))      // Optional(7)
print(smallerDate.fullDistance(from: biggerDate, resultIn: .hour))      // Optional(69441)
print(biggerDate.fullDistance(from: smallerDate, resultIn: .hour))      // Optional(-69441)

print(smallerDate.distance(from: biggerDate, only: .day))               // -2
print(biggerDate.distance(from: smallerDate, only: .day))               // 2
print(smallerDate.distance(from: biggerDate, only: .year))              // -7
print(biggerDate.distance(from: smallerDate, only: .year))              // 7
print(smallerDate.distance(from: biggerDate, only: .hour))              // -9
print(biggerDate.distance(from: smallerDate, only: .hour))              // 9

print(smallerDate.hasSame(.day, as: biggerDate))                        // false
print(biggerDate.hasSame(.second, as: smallerDate))                     // true