Sorting array of date from newest to oldest in Swift 4

Question

I am curious how to sort dates in form of Strings in an array. Most likely I would leave them in the same array and sort them the right way. Many attempts I have seen are with two. Also, they weren't the right time format so I want to know how to sort it with the "dd.MM.yyyy" format. Most likely with only the last two numbers of the year. Is that possible?

Here is what I did. I want it to take the date in the struct to sort:

import UIKit

struct Post {
var title: String
var date: String
var user: String
}

var uploadTimes = [Post(title: "Hello", date: "02.10.2018", user: "Roman"),
                Post(title: "Hi", date: "01.10.2018", user: "Roman"),
                Post(title: "", date: "05.09.2018", user: "")]


uploadTimes = uploadTimes.map{ $0.components(separatedBy: ".").reversed().joined(separator: ".")}
print(uploadTimes)
//["2002.02.02", "2002.02.03", "2002.02.05", "2002.02.04"]


let isoFormatter = ISO8601DateFormatter()
isoFormatter.formatOptions = [.withFullDate,]


let dates = uploadTimes.compactMap { isoFormatter.date(from: $0) }
print(dates)
let sortedDates = dates.sorted { $0 > $1 }
print(sortedDates)

"Value of type 'ISO8601DateFormatter' has no member 'dateFormat'" - this one for example — Thomas22, Dec 11 '18 at 11:52
That's not ISO8601. `let formatter = DateFormatter(); formatter.dateFormat = "dd.MM.yyyy"` — Larme, Dec 11 '18 at 11:53
Well that's a pre configured formatter as it's name suggests. — Desdenova, Dec 11 '18 at 11:53
You don't need to map them to date objects and back to sort them btw. Take a look at these https://stackoverflow.com/questions/53719381/about-comparing-and-generating-character-strings/53719671?r=SearchResults#53719671 https://stackoverflow.com/questions/53704110/ambiguous-reference-to-member-filter-swift4/53704173?r=SearchResults#53704173 — Rakesha Shastri, Dec 11 '18 at 12:04

mlidal · Answer 1 · 2018-12-11T12:01:51.090

8

You can't specify the date format for an ISO8601DateFormatter, it only accepts dates in the normal ISO format.

If you replace it with a normal DateFormatter() you can specify date format. See below code:

var uploadTimes = ["02.02.2002","03.02.2002","05.02.2002","04.02.2002"]

print(uploadTimes)

let isoFormatter = DateFormatter()
isoFormatter.dateFormat = "dd.MM.yyyy"

let dates = uploadTimes.compactMap { isoFormatter.date(from: $0) }

let sortedDates = dates.sorted { $0 > $1 }

print(sortedDates)

let dateStrings = sortedDates.compactMap { isoFormatter.string(from: $0)}

print(dateStrings)

edited Dec 11 '18 at 12:01

answered Dec 11 '18 at 11:53

mlidal

1,111
14
27

It prints out the actual date objects. I've added code to convert back into strings of the original format – mlidal Dec 11 '18 at 12:02

E.Coms · Accepted Answer · 2018-12-17T20:10:40.327

This is another answer with an updated POST structure.

struct Post {
var title: String
var date: String
var user: String
}

extension Post{
static  let isoFormatter : ISO8601DateFormatter = {
    let formatter =  ISO8601DateFormatter()
        formatter.formatOptions = [.withFullDate,]
    return formatter
   }()

var dateFromString : Date  {
    let  iSO8601DateString = date.components(separatedBy: ".").reversed().joined(separator: ".")
    return  Post.isoFormatter.date(from: iSO8601DateString)!
}
}

var uploadTimes = [Post(title: "", date: "05.09.2018", user: ""),
               Post(title: "Hello", date: "02.10.2018", user: "Roman"),
               Post(title: "Hi", date: "01.10.2018", user: "Roman"),
               ]

//sort dates
let dates = uploadTimes.compactMap { $0.dateFromString }
print(dates)
let sortedDates = dates.sorted { $0 > $1 }
print(sortedDates)

//sort posts
let sortedPost = uploadTimes.sorted{ $0.dateFromString > $1.dateFromString  }
print(sortedPost)

If the format is hh:mm dd.MM.yyyy . The updated answer is like this:

extension Post{
static  let isoFormatter : ISO8601DateFormatter = {
    let formatter =  ISO8601DateFormatter()
        formatter.formatOptions = [.withInternetDateTime]
    return formatter
   }()

   var dateFromString : Date  {

  let components = date.components(separatedBy: " ")
  let  iSO8601DateString =
        (components.last!).components(separatedBy: ".").reversed().joined(separator: ".") + "T" + (components.first!) + ":00+00:00"
    return  Post.isoFormatter.date(from: iSO8601DateString)!
   }
}

 var uploadTimes = [Post(title: "", date: "01:20 05.09.2018", user: ""),
               Post(title: "Hello", date: "01:21 02.10.2018", user: "Roman"),
               Post(title: "Hi", date: "01:22 02.10.2018", user: "Roman"),
               ]

I noticed that posts with the same dates will be sorted under each other. So now the newest Post of the same day will be displayed under the other new ones. So I thought about adding a hour and minute display. Can you maybe expand your code so it will compare those to? — Thomas22, Dec 13 '18 at 10:35
in my case it is sorting fine but not updating value in backend and sometime its not sorting. Any solution??? — Mr Abbasi, Mar 03 '21 at 10:59

score 1 · Answer 3 · answered Dec 11 '18 at 16:40

If you insist in using the ISODateFormatter, you may have to change to format of input as they assume an "yyyy.MM.dd" format.

 import UIKit

 var uploadTimes = ["02.02.2002","03.02.2002","05.02.2002","04.02.2002"]
 uploadTimes = uploadTimes.map{ $0.components(separatedBy: ".").reversed().joined(separator: ".")}
 print(uploadTimes)
  //["2002.02.02", "2002.02.03", "2002.02.05", "2002.02.04"]


 let isoFormatter = ISO8601DateFormatter()
 isoFormatter.formatOptions = [.withFullDate,]


 let dates = uploadTimes.compactMap { isoFormatter.date(from: $0) }
 print(dates)
 let sortedDates = dates.sorted { $0 > $1 }
 print(sortedDates)

I do not insist in using it. Actually I think it is really bulky. Do you have alternatives? — Thomas22, Dec 12 '18 at 09:46

Sorting array of date from newest to oldest in Swift 4

3 Answers3