swift - add tableview pagination of posts from reddit API - ios

Question

I'm getting data from Reddit API and displaying reddit posts in the tableview. I want to load 5 (for example) posts from api at a time and display them, and then load next 5 posts when the user scroll down to the last fifth cell.
Maybe I need to change my logic of getting posts from api. Please advice. Thank you!
I'm using MVVM. Populate tableview cells with posts data in TableViewController:
override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "postCell") as! PostTableViewCell
vm.getPost(at: indexPath.row) { post in
guard let post = post else { print("No post"); return }
print(post)
DispatchQueue.main.async {
cell.usernameLabel.text = post.username
cell.domainLabel.text = post.domain
cell.titleLabel.text = post.title
cell.detailsLabel.text = post.text
cell.postImage.sd_setImage(with: URL(string: "\(post.imageURL)"))
cell.timePassedLabel.text = post.createdHoursAgo
cell.ratingButton.setTitle("\(post.rating)", for: .normal)
cell.commentsButton.setTitle("\(post.comments)", for: .normal)
}
// pagination
}
return cell
}
Get one post:
class PostViewModel {
var limit = 30
let sub = "ios"
var portion = 5
var post: RedditPost?
func getPost(at postIndex: Int, completion: (#escaping (_ data: RedditPost?) -> Void)) {
UseCase().createPosts(sub: sub, limit: limit) { posts in
// there are not so many posts on reddit as you asked for (as limit)
if self.limit > posts.count {
print("Error: Number of demanded posts are bigger than available on Reddit")
completion(nil)
} else {
let post = posts[postIndex]
self.post = post
completion(post)
}
}
}
}
Get all posts from API:
class UseCase {
func createPosts(sub: String, limit: Int, completion: (#escaping (_ data: [RedditPost]) -> Void)) {
Repository().fillPostsArray(sub: sub, limit: limit) { (redditPosts: [RedditPost]) in
completion(redditPosts)
}
}
}

Answer 1

the first API call should be made from the viewDidLoad method and reload the tableView when the response comes.
override func viewDidLoad() {
super.viewDidLoad()
setupTableView()
loadPostsFromRedit()
}
private func loadPostsFromRedit() {
vm.getPost(at: indexPath.row) { [weak self] posts in
guard let self = self, let post = posts else {
return
}
print(posts)
self.post = posts
DispatchQueue.main.async {
self.tableView.reloadData()
}
}
Pagination:
You can use the willDisplayCell method to check if the user has reached the end of the tableView and call the API to load the next page
func tableView(_ tableView: UITableView, willDisplay cell: UITableViewCell, forRowAt indexPath: IndexPath) {
if post.count == indexPath.row - 1 {
vm.loadMorePosts()
}
}
Note: you also need to pass the page index to redit API to return the correct page response. Refer this tutorial for more details https://www.raywenderlich.com/5786-uitableview-infinite-scrolling-tutorial