Pagination with Firebase firestore - swift 4

Question

I\'m trying to paginate data (infinitely scroll my tableview) using firestore. I\'ve integrated the code google gives for pagination as best I can, but I\'m still having problem

Answer 1

A little late in the game, but I would like to share how I do it, using the query.start(afterDocument:) method.

class PostsController: UITableViewController {

    let db = Firestore.firestore()

    var query: Query!
    var documents = [QueryDocumentSnapshot]()
    var postArray = [Post]()

    override func viewDidLoad() {
        super.viewDidLoad()

        query = db.collection("myCollection")
                  .order(by: "post", descending: false)
                  .limit(to: 15)

        getData()
    }

    func getData() {
        query.getDocuments() { (querySnapshot, err) in
            if let err = err {
                print("Error getting documents: \(err)")
            } else {
                querySnapshot!.documents.forEach({ (document) in
                    let data = document.data() as [String: AnyObject]

                    //Setup your data model

                    let postItem = Post(post: post, id: id)

                    self.postArray += [postItem]
                    self.documents += [document]
                })
                self.tableView.reloadData()
            }
        } 
    }

    func paginate() {
        //This line is the main pagination code.
        //Firestore allows you to fetch document from the last queryDocument
        query = query.start(afterDocument: documents.last!)
        getData()
    }

    override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return postArray.count
    }

    override func tableView(_ tableView: UITableView, willDisplay cell: UITableViewCell, forRowAt indexPath: IndexPath) {
        // Trigger pagination when scrolled to last cell
        // Feel free to adjust when you want pagination to be triggered
        if (indexPath.row == postArray.count - 1) {
            paginate()
        }
    }
}

Result like so:

Here is a reference.