When to call function that sorts Array in Swift 4?

Question

I made a function that sorts an Array and reorders a TableView (I followed this post). I populate the array through an API.

When or where is best to call the sorting function? When I call it from ViewDidLoad or ViewDidAppear the Array is still empty, so nothing happens.

func sort(){

    self.myArray = myArray.sorted(by: {$0.rank < $1.rank })
    self.tableView.reloadData()

}

When does the array that needs to be sorted get populated in the first place ? — humblePilgrim, May 08 '18 at 07:59
When you never call your sort function the array not nil, right ? — A.Munzer, May 08 '18 at 08:03
Nothing happens so when I want to print the first element of the array, the app crashes because it is not populated yet. This is the crash error: Thread 1: Fatal error: Index out of range — Maruta, May 08 '18 at 08:44
@humblePilgrim I am not sure, I wish I know this.. I wish I know when it finishes populating so I can sort it. Is a tableview in a UIViewController, and it loads when opening the app — Maruta, May 08 '18 at 14:24
Ok.. what is the source of your data ? Do you get it from a web service ? — humblePilgrim, May 09 '18 at 05:22
@humblePilgrim yes, is from a web service. I would like to know when is the tableview completely loaded. If I try to sort it pushing a button, it works, but how can I avoid that? thanks a lot!! — Maruta, May 10 '18 at 05:33
If you know when you have got the data, then you can just check if the array is valid (not nil), sort the array and call reload data? — humblePilgrim, May 10 '18 at 12:02

score 0 · Answer 1 · answered May 08 '18 at 07:59

0

Call your function in ViewDidLoad but without reload table view data

func sort(){
    self.myArray = myArray.sorted(by: {$0.rank < $1.rank })    
}

answered May 08 '18 at 07:59

A.Munzer

1,890
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Mostafa Sultan · Answer 2 · 2018-05-08T08:20:51.140

0

This is a tableView problem, check your delegate, data source and IB connections, nothing is wrong with the sorting as long as the array is not = nil (make sure of that)

edited May 08 '18 at 08:20

answered May 08 '18 at 08:00

Mostafa Sultan

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score 0 · Answer 3 · answered May 08 '18 at 08:14

0

Check you crash log, nothing wrong with this code

answered May 08 '18 at 08:14

Manish Mahajan

2,062
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score 0 · Answer 4 · answered May 08 '18 at 08:25

0

I have no idea what you're using this sort for, so this may not be useful, but you can add a nil check at the top and init a new empty array if it the array is nil.

func sort(){
    if self.myArray == nil {
        self.myArray = [YourArrayType]()
    }
    self.myArray = myArray.sorted(by: {$0.rank < $1.rank })
    self.tableView.reloadData()

}

You can also declare the array optional (private var myArray: [Your ArrayType]?) or initialize it upon declaration (private var myArray = [YourArrayType]()). The first lets you call any method on the array with a ? and it won't execute if the array is nil, the other one makes sure the array is not nil but rather just empty.

answered May 08 '18 at 08:25

kevin

442
3
13

thank you! I tried the first one and still nothing happens with the tableview. Is not nil, but empty. It seems that it needs time to load. And I am doing this test with only 3 elements on the tableview, is not that big.. – Maruta May 08 '18 at 09:03
@Maruta I don't know how you load your tableview data, but a very common way is to load some data from an API and use it to populate the tableview. If something like that is your case you can call `tableView.reloadData()` after finishing your data fetch to signal the tableview to call all its delegate functions again. – kevin May 08 '18 at 09:09
yes I am using an API and I also reloadData after data fetch. But where would you call the func sort() ? Everywhere I call it (except from an IBAction button) the array is not filled yet – Maruta May 08 '18 at 14:15

score 0 · Accepted Answer · answered May 13 '18 at 02:54

Finally what worked was calling the sorting function just after the array is created and reloading the tableview.

override func viewDidLoad() {
super.viewDidLoad()
getData()
}

func getData() {     

 Alamofire.request(apiURL).validate().responseJSON() { response in
            switch response.result {
            case .success:
                if let value = response.result.value {
                    let json = JSON(value)
                    let users = json.arrayValue
                    for item in users{
                        let temp = User(json: item)
                        self.myArray.append(temp)
                    }

                    self.tableView.reloadData()

                    self.sort()     //<---here

                }
            case .failure(let error):
                print(error)
            }
        }

func sort(){

    self.myArray = myArray.sorted(by: {$0.rank < $1.rank })
    self.tableView.reloadData()

}

When to call function that sorts Array in Swift 4?

5 Answers5