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!

Answer 1

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()

Answer 2

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
}

Answer 3

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!

Answer 4

如果您希望不重新加载就更新表格视图，则必须使用func insertRows（在indexPaths：[IndexPath]，动画：UITableViewRowAnimation）。您应该查看此文档，以更好地了解如何实现任务： https ：//developer.apple.com/library/content/documentation/UserExperience/Conceptual/TableView_iPhone/ManageInsertDeleteRow/ManageInsertDeleteRow.html