Swift: Compare date by days

问题

I try to compare two days ignoring time. So I use

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

BUT when transfering the string date to Date type, it is transformed to UTC. So it will be "moved" from 1.1.2016 0:05 to 31.12.2015 11:05 pm. When comparing daywise, this includes only the remaining hour. Before conversion it was 24 hours. Any idea to handle this issue without much effort?

Additionally: The code:

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

回答1:

Details

Xcode 10.1 (10B61, Swift 4.2
Xcode 10.2.1 (10E1001), Swift 5

Idea

base on usage dateComponents(_:from:to:) function

Solution

import Foundation

extension Date {

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

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

    func hasSame(_ component: Calendar.Component, as date: Date) -> Bool {
        return self.compare(with: date, only: component) == 0
    }
}

Full Sample

Do not forget to put here the Solution code (look above)

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

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

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

来源：https://stackoverflow.com/questions/40633139/swift-compare-date-by-days

标签

swift

date

compare

utc