Swift 4 tableView API Pagination

Question

I have successfully parsed and decoded the JSON data and it displays in the console. I don't know how I would set up pagination with the api and display all of the data when I scroll down on the tableView. The API I'm using is https://rickandmortyapi.com/api/character/. Thank you for all your help in advance!

This is the code in my main ViewController

import UIKit

struct PagedCharacters: Codable {
    struct Info: Codable {
        let count: Int
        let pages: Int
        let next: String
        let prev: String
    }

    struct Results: Codable {
        let name: String
        let status: String
        let species: String
    }

    let info: Info
    let results: [Results]

}


class ViewController: UIViewController, UITableViewDataSource, UITableViewDelegate {

    @IBOutlet var uiTableView: UITableView!

    override func viewDidLoad() {
        super.viewDidLoad()
        getRickAndMortyData()


        self.uiTableView.dataSource = self
        self.uiTableView.delegate = self

        // Do any additional setup after loading the view.
    }

    func getRickAndMortyData() {

        //create instance of the url
        let url = "https://rickandmortyapi.com/api/character/"

        //construct the url, use guard to avoid nonoptional
        guard let urlObj = URL(string: url) else
        { return }

        //fetch data
        URLSession.shared.dataTask(with: urlObj) {(data, response, error) in

            //to avoid non optional in JSONDecoder
            guard let data = data else { return }

            do {
                //decode object
                let downloadedRickAndMorty = try JSONDecoder().decode(PagedCharacters.self, from: data)
             DispatchQueue.main.async {
                    self.uiTableView.reloadData()
                }
               print(downloadedRickAndMorty)

            } catch {
                print(error)

            }

            }.resume()

    }


    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        // #warning Incomplete implementation, return the number of rows
        return 0
    }

    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        guard let cell = tableView.dequeueReusableCell(withIdentifier: "rickandmortyCell") as? CharacterTableViewCell else { return UITableViewCell() }

        cell.nameLabel.text = "Name: " + PagedCharacters.Results[indexPath.row].name

        return cell
    }


}

This is my tableviewcell class

import UIKit

class CharacterTableViewCell: UITableViewCell {

    @IBOutlet weak var nameLabel: UILabel!


    override func awakeFromNib() {
        super.awakeFromNib()
        // Initialization code
    }

    override func setSelected(_ selected: Bool, animated: Bool) {
        super.setSelected(selected, animated: animated)

        // Configure the view for the selected state
    }

}

This is the data I'm getting in my console when the parsed data is printed. I'm still not getting all the data from the different pages.

PagedCharacters(info: API_Practice.PagedCharacters.Info(count: 493, pages: 25, next: "https://rickandmortyapi.com/api/character/?page=2", prev: ""), results: [API_Practice.PagedCharacters.Results(name: "Rick Sanchez", status: "Alive", species: "Human"), API_Practice.PagedCharacters.Results(name: "Morty Smith", status: "Alive", species: "Human"), API_Practice.PagedCharacters.Results(name: "Summer Smith", status: "Alive", species: "Human"), API_Practice.PagedCharacters.Results(name: "Beth Smith", status: "Alive", species: "Human"), API_Practice.PagedCharacters.Results(name: "Jerry Smith", status: "Alive", species: "Human"), API_Practice.PagedCharacters.Results(name: "Abadango Cluster Princess", status: "Alive", species: "Alien"), API_Practice.PagedCharacters.Results(name: "Abradolf Lincler", status: "unknown", species: "Human"), API_Practice.PagedCharacters.Results(name: "Adjudicator Rick", status: "Dead", species: "Human"), API_Practice.PagedCharacters.Results(name: "Agency Director", status: "Dead", species: "Human"), API_Practice.PagedCharacters.Results(name: "Alan Rails", status: "Dead", species: "Human"), API_Practice.PagedCharacters.Results(name: "Albert Einstein", status: "Dead", species: "Human"), API_Practice.PagedCharacters.Results(name: "Alexander", status: "Dead", species: "Human"), API_Practice.PagedCharacters.Results(name: "Alien Googah", status: "unknown", species: "Alien"), API_Practice.PagedCharacters.Results(name: "Alien Morty", status: "unknown", species: "Alien"), API_Practice.PagedCharacters.Results(name: "Alien Rick", status: "unknown", species: "Alien"), API_Practice.PagedCharacters.Results(name: "Amish Cyborg", status: "Dead", species: "Alien"), API_Practice.PagedCharacters.Results(name: "Annie", status: "Alive", species: "Human"), API_Practice.PagedCharacters.Results(name: "Antenna Morty", status: "Alive", species: "Human"), API_Practice.PagedCharacters.Results(name: "Antenna Rick", status: "unknown", species: "Human"), API_Practice.PagedCharacters.Results(name: "Ants in my Eyes Johnson", status: "unknown", species: "Human")])

If you need anything else please let me know. Thank you!

Answer 1

There were many flaws in your logic, so I have rewritten it with minimal changes. Now it will serve your purpose.

import UIKit
struct PagedCharacters: Codable {
    let info: Info
    let results: [Results]

}
struct Info: Codable {
    let count: Int
    let pages: Int
    let next: String
    let prev: String
}

struct Results: Codable {
    let name: String
    let status: String
    let species: String
}

And here is the code for view controller class:

class ViewController: UIViewController, UITableViewDataSource, UITableViewDelegate {

    @IBOutlet var uiTableView: UITableView!
    var aryDownloadedData:[Results]?
    var nextPageUrl:String!

    override func viewDidLoad() {
        super.viewDidLoad()
        getIntitalRickAndMortyData()


        self.uiTableView.dataSource = self
        self.uiTableView.delegate = self

        // Do any additional setup after loading the view.
    }
    func getIntitalRickAndMortyData(){
        aryDownloadedData = []
        //here first page is next page
        nextPageUrl = "https://rickandmortyapi.com/api/character/"
        getRickAndMortyData()
    }

    func getRickAndMortyData() {

        //construct the url, use guard to avoid nonoptional
        guard let urlObj = URL(string: nextPageUrl) else
        { return }

        //fetch data
        URLSession.shared.dataTask(with: urlObj) {[weak self](data, response, error) in

            //to avoid non optional in JSONDecoder
            guard let data = data else { return }

            do {
                //decode object
                let downloadedRickAndMorty = try JSONDecoder().decode(PagedCharacters.self, from: data)
                self?.aryDownloadedData?.append(contentsOf: downloadedRickAndMorty.results)
                self?.nextPageUrl = downloadedRickAndMorty.info.next

                DispatchQueue.main.async {
                    self?.uiTableView.reloadData()
                }
                print(self?.aryDownloadedData as Any)

            } catch {
                print(error)

            }

            }.resume()

    }


    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return self.aryDownloadedData?.count ?? 0
    }

    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {

        if let count = aryDownloadedData?.count, count>1{
            let lastElement = count - 1
            if indexPath.row == lastElement {
                //call get api for next page
                getRickAndMortyData()
            }
        }

        guard let cell = tableView.dequeueReusableCell(withIdentifier: "rickandmortyCell") as? CharacterTableViewCell else { return UITableViewCell() }

        cell.nameLabel.text = "Name: " + (self.aryDownloadedData?[indexPath.row].name ?? "default")

        return cell
    }
}