Swift4 - Pagination - ios

Question

I'm new in developing ios app. Still dont know much. I successfully can display the articles well from first page only but fail to show other articles from other page when I scroll-up to view more. I really need help if somebody knows how to do pagination from my collection View. Below is the picture of my api that I use.
And below is my code where i get the data from api -- (Artikel.swift)
import Foundation
import Alamofire
import SwiftyJSON
import os.log
struct Artikel: ServiceCompletionHandler {
static func getCategories (completionHandler: #escaping ArrayCompletionHandler) {
let headers: HTTPHeaders = [
"Accept": "application/json"
]
let parameters: Parameters = [
"secret_key": Config.api_key
]
Alamofire.request("\(Config.server_address)/article-categories", method: .post, parameters: parameters, headers: headers)
.responseJSON { (response) -> Void in
switch response.result {
case .success:
let json = JSON(response.result.value!)
if json["data"].exists() {
if let data = json["data"]["data"].array {
completionHandler(data, nil)
} else {
completionHandler([], nil)
}
} else {
completionHandler([], nil)
}
case .failure(let error):
print(error)
completionHandler([], "Network error has occured.")
}
}
}
static func getArticles(_ category_id: Int, completionHandler: #escaping ArrayCompletionHandler) {
let headers: HTTPHeaders = [
"Accept": "application/json",
"secret-key": Config.api_key]
let value: Int = category_id
let newcategory = String(describing: value)
// var nextpages = NewsSectionViewController.url
let new_api = Config.server_addforarticle + newcategory
Alamofire.request(new_api, method: .get, headers: headers)
.responseJSON { (response) -> Void in
switch response.result {
case .success:
let json = JSON(response.result.value!)
// dump(json, name: "testing")
if let articles = json["articles"]["data"].array {
completionHandler(articles, nil)
}else{
completionHandler([], nil)
}
case .failure(let error):
print(error)
completionHandler([], "Network error has occured.")
}
}
}
}
and here where i display my articles. But yeah, I cant do pagination it stuck to 4-5 articles only. I just dont have any idea how to do what I did in my android version.
NewsSectionViewController.swift
import UIKit
import SwiftyJSON
import AlamofireImage
protocol NewsSectionViewControllerDelegate {
func updateArrowPosition()
}
class NewsSectionViewController: UIViewController, UICollectionViewDataSource, UICollectionViewDelegateFlowLayout {
// MARK: - Variables
var itemIndex: Int = 0
var category:JSON!
var stories:[JSON] = []
var delegate: NewsSectionViewControllerDelegate?
// MARK: - Views
#IBOutlet var titleLabel: UILabel!
#IBOutlet var collectionView: UICollectionView!
#IBOutlet var loadingIndicator: UIActivityIndicatorView!
// MARK: - Constraint
#IBOutlet var titleTopConstraint: NSLayoutConstraint!
override func viewDidLoad() {
super.viewDidLoad()
self.titleLabel.text = category["name"].stringValue.uppercased()
self.collectionView.contentInset = UIEdgeInsetsMake(0, 0, 114, 0)
if #available(iOS 11.0, *) {
if ((UIApplication.shared.keyWindow?.safeAreaInsets.top)! > CGFloat(0.0)) {
self.collectionView.contentInset = UIEdgeInsetsMake(0, 0, 173, 0)
self.collectionView.scrollIndicatorInsets = UIEdgeInsetsMake(0, 0, 173, 0)
}
}
self.loadingIndicator.startAnimating()
Artikel.getArticles(category["id"].intValue) {
(articles, error) in
self.loadingIndicator.stopAnimating()
if error == nil {
self.stories = articles
self.collectionView.reloadData()
}
}
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
// MARK: - Collection View
func numberOfSections(in collectionView: UICollectionView) -> Int {
return 1
}
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return self.stories.count - 1
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
var cell: NewsItemCollectionViewCell?
let item = stories[indexPath.row + 1]
if indexPath.row == 0 {
cell = collectionView.dequeueReusableCell(withReuseIdentifier: "BigCell", for: indexPath) as? NewsItemCollectionViewCell
} else {
cell = collectionView.dequeueReusableCell(withReuseIdentifier: "SmallCell", for: indexPath) as? NewsItemCollectionViewCell
}
cell!.titleLabel.text = item["title"].stringValue
if let thumbUrlString = item["banner_url_large"].string {
if let thumbUrl = URL(string: thumbUrlString) {
cell?.coverImageView.af_setImage(withURL: thumbUrl)
}
}
let wpDateFormatter = DateFormatter()
wpDateFormatter.dateFormat = "yyyy-MM-dd HH:mm:ss"
let dayDateFormatter = DateFormatter()
dayDateFormatter.dateStyle = .medium
dayDateFormatter.doesRelativeDateFormatting = true
let date = wpDateFormatter.date(from: item["date_publish_web"].stringValue)!
cell!.timestampLabel.text = dayDateFormatter.string(from: date)
return cell!
}
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
let story = self.stories[indexPath.row + 1]
let newsContents = self.storyboard?.instantiateViewController(withIdentifier: "NewsContent") as! NewsContentViewController
newsContents.story = story
newsContents.title = self.category["name"].string
self.navigationController?.pushViewController(newsContents, animated: true)
}
func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
if indexPath.row == 0 {
let width = UIScreen.main.bounds.width - 30
return CGSize(width: width, height: 385 - 20)
} else {
let width = (UIScreen.main.bounds.width - 45) / 2
return CGSize(width: width, height: 210)
}
}
// MARK: - ScrollView
func scrollViewDidScroll(_ scrollView: UIScrollView) {
if scrollView == self.collectionView {
self.titleTopConstraint.constant = 30 - scrollView.contentOffset.y
}
if let delegate = self.delegate {
delegate.updateArrowPosition()
}
}
/*
// MARK: - Navigation
// In a storyboard-based application, you will often want to do a little preparation before navigation
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
// Get the new view controller using segue.destinationViewController.
// Pass the selected object to the new view controller.
}
*/
}
Any help I really appreciated and thank you in advance :)

Answer 1

In NewsSectionViewController:
1) add global variables:
a) var nextPageUrl: String? ;
b) let numberOfPagination = 5 (5 it's a number of items in one url page);
c) add variable hasMoreItems
var hasMoreItems: Bool {
get {
guard let count = nextPageUrl?.count, count > 0 else {
return false
}
return true
}
}
d) add variable numberOfItems
var numberOfItems: Int {
get {
return secrets.count
}
}
2) change this line self.stories = articles to self.stories += articles
3) add function for pagination:
func tableView(_ tableView: UITableView, willDisplay cell: UITableViewCell, forRowAt indexPath: IndexPath) {
if (indexPath.item + 1 == numberOfItems) && ((indexPath.item + 1) % numberOfPagination == 0) {
if self.presenter.hasMoreItems {
self.loadData()
}
}
}
f) add func loadData()
func loadData() {
Artikel.getArticles(category["id"].intValue, nextPageUrl: nextPageUrl) {
(articles, error) in
self.loadingIndicator.stopAnimating()
if error == nil {
self.stories = articles
self.collectionView.reloadData()
}
}
}
In Artikel:
1) change getArticles function
static func getArticles(_ category_id: Int, nextPageUrl: String?, completionHandler: #escaping ArrayCompletionHandler) {
//...
let new_api = nextPageUrl ?? Config.server_addforarticle + newcategory
//...
}
2) in this function you can return nextPageUrl value in ArrayCompletionHandler