How to compare 2 arrays and append last items to second array iOS Swift 3

Question

Let's say i have a firstArray of PFObject[](from Parse SDK), and it has 7 items, i make a secondArray out of firstArray:

secondArray = firstArray

then i call a query to the database to retrieve updated data, they are now 10 items in firstArray.

I do something like this:

if firstArray.count > secondArray.count {
      let lastItems = firstArray.count - secondArray.count
     // lastItems = 3
}

How do i append those 3 last items to the end of the secondArray in their specific order?

secondArray append item 8

secondArray append item 9

secondArray append item 10

I don't want to reloadData(), i just want to add the last 3 rows to my TableView like WhatsApp does, for example, otherwise the TableView will scroll to the top.

Thanks!

If you just don't want to scroll to the top, one way is to programmatically scroll to bottom immediately after reloadData(), e.g. with this http://stackoverflow.com/questions/952412/uiscrollview-scroll-to-bottom-programmatically — aunnnn, Feb 28 '17 at 07:20

score 2 · Answer 1 · answered Feb 28 '17 at 07:26

First append data to second array

secondArray.append(firstArray[index])

Then

self.yourTableView.beginUpdates()
var insertedIndexPaths = [indexpath_where_you_want_insertData]

self.yourTableView.insertRowsAtIndexPaths(insertedIndexPaths, withRowAnimation: .Fade)
self.yourTableView.endUpdates()

rv7284 · Answer 2 · 2017-02-28T07:08:06.763

1

if firstArray and secondArray are same you can just do

secondArray = firstArray

and if in case you have updated secondArray and wants to append new data only

var counter = 0
while secondArray.count != firstArrayCount {
    secondArray.append(firstArray[firstArray.count+counter])
    counter += 1
    //insert new row in table
}

edited Feb 28 '17 at 07:08

answered Feb 28 '17 at 06:57

rv7284

1,092
9
25

Yes, sorry, I haven't expressed my question correctly, i then need to update my TableView Datasource without reloading all data, only adding the last 3 rows to the end of the table, like WhatsApp does for example, of I call tableView.reloadData() it refreshes the entire TableView and scrolls it to the top – Frank Eno Feb 28 '17 at 07:00

score 1 · Accepted Answer · answered Feb 28 '17 at 07:09

1

Since you ask for a way to append it, this should work.

if firstArray.count > secondArray.count {
    for i in secondArray.count..<firstArray.count {
        secondArray.append(firstArray[i])
    }
}

Hope this helps!

answered Feb 28 '17 at 07:09

GerardoMR

81
3

score 0 · Answer 4 · answered Feb 28 '17 at 07:24

0

If you wish to update your table view without reloading it, you'll have to use func insertRows(at indexPaths: [IndexPath], with animation: UITableViewRowAnimation) You should look at this doc for better understanding of how to implement your task: https://developer.apple.com/library/content/documentation/UserExperience/Conceptual/TableView_iPhone/ManageInsertDeleteRow/ManageInsertDeleteRow.html

answered Feb 28 '17 at 07:24

Eugene Svaro

394
2
5

Yes, I know how to add rows to a tableView, i just needed the code to append last items to my secondArray, like the answer below this one ;) – Frank Eno Feb 28 '17 at 07:37

How to compare 2 arrays and append last items to second array iOS Swift 3

4 Answers4