229 Views 9 Replies
      Latest reply on Nov 1, 2016 3:16 AM by eskimo
      Nyt Liv Ivs Level 1 Level 1 (0 points)
      Nyt Liv Ivs Oct 20, 2016 9:28 AM

        I have three nsmutablearrays and the are all connected.

         

        In one I have a lot of dates.

        In another I have a lot of text for each date.

        And in the last one I have a lot of image paths for for each date.

         

        Now I want to sort the one with date sp that when I put them info my UICollectionView the date are shown sorted.

         

        How do I sorted my NSMUtableArray with dates and how do I sort the other NSMutableArrays so that the text and path still is in the same position as the date for them?

         

        I hope someone can help me.

         

        I'm using Swift 3.

        • Re: Sorting multiply nsmutablearrays
          eskimo Apple Staff Apple Staff (10,065 points)
          eskimo Oct 20, 2016 3:26 PM (in response to Nyt Liv Ivs)

          I have three nsmutablearrays and the are all connected.

          This approach is less than ideal.  It would be better to put the data for each element into a struct and then store a (Swift) array of those structures.  This change will solve your current problem and generally make things nicer.

          If you can’t do that then the standard solution for this is to be a fourth array that contains a struct with two fields:

          • the sort key (the date in this case)

          • an index into the other arrays

          You can then sort this array and follow the index to get to your real data.

          Share and Enjoy
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          Quinn “The Eskimo!”
          Apple Developer Relations, Developer Technical Support, Core OS/Hardware
          let myEmail = "eskimo" + "1" + "@apple.com"

            • Re: Sorting multiply nsmutablearrays
              eskimo Apple Staff Apple Staff (10,065 points)
              eskimo Oct 21, 2016 2:11 AM (in response to eskimo)

              … is to be a fourth array …

              … is to create a fourth array …

              Share and Enjoy
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              Quinn “The Eskimo!”
              Apple Developer Relations, Developer Technical Support, Core OS/Hardware
              let myEmail = "eskimo" + "1" + "@apple.com"

                • Re: Sorting multiply nsmutablearrays
                  Nyt Liv Ivs Level 1 Level 1 (0 points)
                  Nyt Liv Ivs Oct 21, 2016 3:32 AM (in response to eskimo)

                  Thanks I'l try the fourth array

                  • Re: Sorting multiply nsmutablearrays
                    Nyt Liv Ivs Level 1 Level 1 (0 points)
                    Nyt Liv Ivs Oct 23, 2016 12:43 PM (in response to eskimo)

                    Can you point me in the right direction with struct and the fourth NSMutableArray?

                      • Re: Sorting multiply nsmutablearrays
                        eskimo Apple Staff Apple Staff (10,065 points)
                        eskimo Oct 24, 2016 4:04 AM (in response to Nyt Liv Ivs)

                        Actually, I made this sound more complex than it really is.  All you need to do is create an array of indexes into the arrays and sort those.  For example:

                        let names    = ["Lancelot", "Robin", "Galahad", "Arthur"]
let questions = ["favourite colour", "capital of assyria", "favourite colour", "airspeed velocity of an unladen swallow"]
let answers  = ["blue", "I don't know that", "blue no yellow", "african or european?"]

let sortedIndices = names.indices.sorted(by: { (lhsIndex, rhsIndex) -> Bool in
    return names[lhsIndex] < names[rhsIndex]
})

for i in sortedIndices {
    print("--")
    print(names[i])
    print(questions[i])
    print(answers[i])
}

                        In this context, names.indices returns 0..<4, that is, the indices of the array.  I then sort those indices by looking at the name values.  The end result is a set of indices that can be used to access any of the arrays.

                        Share and Enjoy
                        —
                        Quinn “The Eskimo!”
                        Apple Developer Relations, Developer Technical Support, Core OS/Hardware
                        let myEmail = "eskimo" + "1" + "@apple.com"

                          • Re: Sorting multiply nsmutablearrays
                            Nyt Liv Ivs Level 1 Level 1 (0 points)
                            Nyt Liv Ivs Oct 31, 2016 3:24 AM (in response to eskimo)

                            Thanks for you reply.

                             

                            I'm using NSMutableArrays and I get an error telling me that it does not know indices.

                             

                            I tried your code and it was sorting but not the way I need it to do.

                             

                            I have an array of dates: "16. aprill 2016", "15. aprill 2016", "17. aprill 2016"

                             

                            And I have an arrays of text for each date: "bla. bla. 1", "bla. bla. 2", "bla. bla. 3"

                             

                            And I have an array of image names: "image1", "image2", "image3"

                             

                            Now I want to sort on the date so that the end result is like this:

                             

                            "15. aprill 2016" - "bla. bla. 2" - "image2"

                            "16. aprill 2016" - "bla. bla. 1" - "image1"

                            "17. aprill 2016" - "bla. bla. 3" - "image3"

                             

                            And when I try your code I don't get the same kind of result.

                              • Re: Sorting multiply nsmutablearrays
                                eskimo Apple Staff Apple Staff (10,065 points)
                                eskimo Oct 31, 2016 6:43 AM (in response to Nyt Liv Ivs)

                                For a standard Swift array the indices property returns a list of indices for the array.  For NSMutableArray the indices are always 0..<array.count.

                                Honestly though, I think you’re way off in the weeds here.  If I were in your shoes I’d use a single Swift array containing a struct rather than multiple NSMutableArray.  This is going to result in nicer (and more Swift-ish) code.

                                Share and Enjoy
                                —
                                Quinn “The Eskimo!”
                                Apple Developer Relations, Developer Technical Support, Core OS/Hardware
                                let myEmail = "eskimo" + "1" + "@apple.com"

                                  • Re: Sorting multiply nsmutablearrays
                                    Nyt Liv Ivs Level 1 Level 1 (0 points)
                                    Nyt Liv Ivs Oct 31, 2016 7:59 AM (in response to eskimo)

                                    I'm not that much into structs

                                    Can you point me in the right direction?

                                      • Re: Sorting multiply nsmutablearrays
                                        eskimo Apple Staff Apple Staff (10,065 points)
                                        eskimo Nov 1, 2016 3:16 AM (in response to Nyt Liv Ivs)

                                        I'm not that much into structs.  Can you point me in the right direction?

                                        Sure.  To continue my previous example, here’s how I’d define a struct to hold all the info for a given knight.

                                        struct Knight {
    var name: String
    var question: String
    var answer: String
}

                                        Here’s how I’d set up an array of those:

                                        let knights: [Knight] = [
    Knight(name: "Lancelot", question: "favourite colour",  answer: "blue"),
    Knight(name: "Robin",    question: "capital of assyria", answer: "I don't know that"),
    Knight(name: "Galahad",  question: "favourite colour",  answer: "blue no yellow"),
    Knight(name: "Arthur",  question: "airspeed velocity of an unladen swallow", answer: "african or european?")
]

                                        and here’s how to get a sorted array from that:

                                        let sortedKnights = knights.sorted(by: { (lhs, rhs) -> Bool in 
    return lhs.name < rhs.name 
})

                                        If you’re starting off with multiple parallel arrays (for example, because that’s how the data is store in a file on disk), it’s relatively straightforward to build your array of structures from those arrays:

                                        let names = ["Lancelot", "Robin", "Galahad", "Arthur"] 
let questions = ["favourite colour", "capital of assyria", "favourite colour", "airspeed velocity of an unladen swallow"] 
let answers = ["blue", "I don't know that", "blue no yellow", "african or european?"] 

let knights = (0..<names.count).map { index in
    return Knight(name: names[index], question: questions[index], answer: answers[index])
}

                                        Structs are a critical part of any Swift app — for example, the bulk of the functionality in the Swift standard library is exposed via structs — so it’s really important that you get to know them.  They are discussed in depth in The Swift Programming Language, and presumably all other tutorial introductions to Swift.

                                        Share and Enjoy
                                        —
                                        Quinn “The Eskimo!”
                                        Apple Developer Relations, Developer Technical Support, Core OS/Hardware
                                        let myEmail = "eskimo" + "1" + "@apple.com"