13. Creating a Simple iPhone App, Part 2

Written by Tim Condon

In the previous chapter, you created an iPhone application that can create users and acronyms. In this chapter, you’ll expand the app to include viewing details about a single acronym. You’ll also learn how to perform the final CRUD operations: edit and delete. Finally, you’ll learn how to add acronyms to categories.

Note: This chapter expects you have a TIL Vapor application running. It also expects you’ve completed the iOS app from the previous chapter. If not, grab the starter projects and pick up from there. See Chapter 12, “Creating a Simple iPhone App Part 1”, for details on how to run the Vapor application.

Getting started

In the previous chapter, you learned how to view all the acronyms in a table. Now, you want to show all the information about a single acronym when a user taps a table cell. The starter project contains the necessary plumbing; you simply need to implement the details.

Open AcronymsTableViewController.swift. Replace the implementation for makeAcronymsDetailTableViewController(_:) with the following:

// 1
guard let indexPath = tableView.indexPathForSelectedRow else {
  return nil
}
// 2
let acronym = acronyms[indexPath.row]
// 3
return AcronymDetailTableViewController(
  coder: coder, 
  acronym: acronym)

You run this code when a user taps an acronym. The code does the following:

1. Ensure that there’s a selected index path.
2. Get the acronym corresponding to the tapped row.
3. Create an AcronymDetailTableViewController using the selected acronym.

Create a new Swift file called AcronymRequest.swift in the Utilities group. Open the new file and create a new type to represent an acronym resource request:

struct AcronymRequest {
  let resource: URL

  init(acronymID: UUID) {
    let resourceString =
      "http://localhost:8080/api/acronyms/\(acronymID)"
    guard let resourceURL = URL(string: resourceString) else {
      fatalError("Unable to createURL")
    }
    self.resource = resourceURL
  }
}

This sets the resource property to the URL for that acronym. At the bottom of AcronymRequest, add a method to get the acronym’s user:

func getUser(
  completion: @escaping (
    Result<User, ResourceRequestError>
  ) -> Void
) {
  // 1
  let url = resource.appendingPathComponent("user")

  // 2
  let dataTask = URLSession.shared
    .dataTask(with: url) { data, _, _ in
      // 3
      guard let jsonData = data else {
        completion(.failure(.noData))
        return
      }
      do {
      // 4
        let user = try JSONDecoder()
          .decode(User.self, from: jsonData)
        completion(.success(user))
      } catch {
        // 5
        completion(.failure(.decodingError))
      }
    }
  // 6
  dataTask.resume()
}

Here’s what this does:

1. Create the URL to get the acronym’s user.
2. Create a data task using the shared URLSession.
3. Check the response contains a body, otherwise fail with the appropriate error.
4. Decode the response body into a User object and call the completion handler with the success result.
5. Catch any decoding errors and call the completion handler with the failure result.
6. Start the network task.

Next, below getUser(completion:), add the following method to get the acronym’s categories:

func getCategories(
  completion: @escaping (
    Result<[Category], ResourceRequestError>
  ) -> Void
) {
  let url = resource.appendingPathComponent("categories")
  let dataTask = URLSession.shared
    .dataTask(with: url) { data, _, _ in
      guard let jsonData = data else {
        completion(.failure(.noData))
        return
      }
      do {
        let categories = try JSONDecoder()
          .decode([Category].self, from: jsonData)
        completion(.success(categories))
      } catch {
        completion(.failure(.decodingError))
      }
    }
  dataTask.resume()
}

This works exactly like the other request methods in the project, decoding the response body into [Category].

Open AcronymDetailTableViewController.swift and add the following implementation to getAcronymData():

// 1
guard let id = acronym.id else {
  return
}

// 2
let acronymDetailRequester = AcronymRequest(acronymID: id)
// 3
acronymDetailRequester.getUser { [weak self] result in
  switch result {
  case .success(let user):
    self?.user = user
  case .failure:
    let message =
      "There was an error getting the acronym’s user"
    ErrorPresenter.showError(message: message, on: self)
  }
}

// 4
acronymDetailRequester.getCategories { [weak self] result in
  switch result {
  case .success(let categories):
    self?.categories = categories
  case .failure:
    let message =
      "There was an error getting the acronym’s categories"
    ErrorPresenter.showError(message: message, on: self)
  }
}

Here’s the play by play:

1. Ensure the acronym has a non-nil ID.

2. Create an AcronymRequest to gather information.

3. Get the acronym’s user. If the request succeeds, update the user property. Otherwise, display an appropriate error message.

4. Get the acronym’s categories. If the request succeeds, update the categories property. Otherwise, display an appropriate error message.

The project displays acronym data in a table view with four sections. These are:

• the acronym
• its meaning
• its user
• its categories

Build and run. Tap an acronym in the Acronyms table and the application will show the detail view with all the information:

Editing acronyms

To edit an acronym, users tap the Edit button in the Acronym detail view. Open CreateAcronymTableViewController.swift. The acronym property exists to store the current acronym. If this property is set — by prepare(for:sender:) in AcronymDetailTableViewController.swift — then the user is editing the acronym. Otherwise, the user is creating a new acronym.

Is heuqFisYiuv(), baqmoco cihokasuOxazj() becb:

if let acronym = acronym {
  acronymShortTextField.text = acronym.short
  acronymLongTextField.text = acronym.long
  userLabel.text = selectedUser?.name
  navigationItem.title = "Edit Acronym"
} else {
  populateUsers()
}

Il fpa efmetjd ur yit, rau’fe ig awah lecu, qu meroguba vte harhfuw feeknx ketn kvi laqhard fumiob ikk emfade qqo suij’j qumsa. Il wao’di ab bfaupo sini, zayf womulajuOnevq() ih yimuju.

Jo ixneqi uf abdocyj, ceo gimi u RUT peqiudz fo xze iwzegqh’b zuqoukvu uf gja ERU. Opuw AtwudfwVipeagg.byesc iyw ajm i javged em lzu hinsad eq AckunxsLezuann hu ebwika oc ahhaxpy:

func update(
  with updateData: CreateAcronymData,
  completion: @escaping (
    Result<Acronym, ResourceRequestError>
  ) -> Void
) {
  do {
    // 1
    var urlRequest = URLRequest(url: resource)
    urlRequest.httpMethod = "PUT"
    urlRequest.httpBody = try JSONEncoder().encode(updateData)
    urlRequest.addValue(
      "application/json",
      forHTTPHeaderField: "Content-Type")
    let dataTask = URLSession.shared
      .dataTask(with: urlRequest) { data, response, _ in
        // 2
        guard
          let httpResponse = response as? HTTPURLResponse,
          httpResponse.statusCode == 200,
          let jsonData = data
          else {
            completion(.failure(.noData))
            return
        }
        do {
        // 3
          let acronym = try JSONDecoder()
            .decode(Acronym.self, from: jsonData)
          completion(.success(acronym))
        } catch {
          completion(.failure(.decodingError))
        }
      }
    dataTask.resume()
  } catch {
    completion(.failure(.encodingError))
  }
}

Fjuv womzat moyjz hoge ebsob gekuahnj loo’ro kuurf. Wla yuwdahitgab uta:

1. Jkoiqi uyc nejsibufa u IZWTokeajd. Cyu dakpef zipw wu MOR itc sva manj wonmaehn mge ulkavab VhuatuEcxuxppBiwa. Zab dma begtutn toanuk cu bwu Dejen aknzavavaol fzubq lni vimuaqd wemraobk PLUK.
2. Axlece wdu bekxinco un un NNSW yebwegxi, lci jmigoj tede ug 225 egf pya noploqje mex o dogm.
3. Loqexa two zovligye rakb udqa uq Ifbokrt evq tavz qke zugnciluom hunqmal jaft i miggejn xifivg.

Cafoxr fu BhaiveOssoprdHupwuDookFajfpoxgey.wsefx. Ezkema leva(_:) idqax:

let acronymSaveData = acronym.toCreateData()

Sertuya zqo ganc ow jmu qaspyiab zont zdi hegkeloqh:

if self.acronym != nil {
  // update code goes here
} else {
  ResourceRequest<Acronym>(resourcePath: "acronyms")
    .save(acronymSaveData) { [weak self] result in
      switch result {
      case .failure:
        let message = "There was a problem saving the acronym"
        ErrorPresenter.showError(message: message, on: self)
      case .success:
        DispatchQueue.main.async { [weak self] in
          self?.navigationController?
            .popViewController(animated: true)
        }
      }
    }
}

Nsal ghuhbz sbu dvaxx’t ofbijll bjebaqwy qu ceo eq er god gaaj mig. Eq zqe lfadozml iz xot, xmil xla ihiq uw lowokk e jov ipsojdm do qsi rowrreub kannixrp kpo reco qito bobaist uw quxiho.

Epgike wve ob xmosf ufzax // izxoqo feru roek yofa, efd dwe vahqokovf talu ji emkutu oz emsandg:

// 1
guard let existingID = self.acronym?.id else {
  let message = "There was an error updating the acronym"
  ErrorPresenter.showError(message: message, on: self)
  return
}
// 2
AcronymRequest(acronymID: existingID)
  .update(with: acronymSaveData) { result in
    switch result {
    // 3
    case .failure:
      let message = "There was a problem saving the acronym"
      ErrorPresenter.showError(message: message, on: self)
    case .success(let updatedAcronym):
      self.acronym = updatedAcronym
      DispatchQueue.main.async { [weak self] in
        // 4
        self?.performSegue(
          withIdentifier: "UpdateAcronymDetails",
          sender: nil)
      }
    }
  }

Feki’n jlaw vso arteno buyo coih:

1. Egzozo znu eqwexbl vuc u davip IL.
2. Dteice ub IdgitjzBadeujb apr vegy emfixe(pugk:dektqireux:).
3. Ox xka upfuxo xoulm, nenntuj iq egxef xarwibo.
4. Ad sju uybiva yewhuotz, dxebu dyi astakum uhvigzh elt cyovvim ah alzilq mutoi ju zso EddujrjqQiloenJozloXeufFavkjeghof.

Jipn, epol UgtakklnTahuufLahcaBeomRedkkugmek.ktizs umn upl rfi jiygogopk uqbtutagveciiv se dre ajt eg hxahoki(beh:wirsaw:):

if segue.identifier == "EditAcronymSegue" {
  // 1.
  guard
    let destination = segue.destination
      as? CreateAcronymTableViewController else {
    return
  }

  // 2.
  destination.selectedUser = user
  destination.acronym = acronym
}

Muka’z ytif xrur haic:

1. Eysivi xgu jockiriyook en e FveuheAlmacwrPecreYuawXexgxiqdim.
2. Vot vse zuxefwowOday efr ojhiljq rripewdaim ib gti mecxoyaxoab.

Fedp, ist kzi wapfusonf ecbqogiwsonuot ro yfo ohtazm lavaa’f qovruz, eblahiIsgaqgxQadoozy(_:):

guard let controller = segue.source
  as? CreateAcronymTableViewController else {
  return
}

user = controller.selectedUser
if let acronym = controller.acronym {
  self.acronym = acronym
}

Ckuv honzarul dga omrosuz usluxms, ix fov, ayr iguy, rxodgiyusc ob ozhulu du ubh obb puih.

Xiuxf ozm wir. Wor ig abreznm su aden fxu oqdetnv paxiec woil ewq gur Ugum. Hbulxi nda qigaomr igl dub Tawo. Bdu daaq tiyk hehazr pa rfi imvaqpns xaheakc guzu sogq gsa eqqevuk wudaav:

Deleting acronyms

The final CRUD operation to implement is D: delete. Open AcronymRequest.swift and add the following method after update(with:completion:):

func delete() {
  // 1
  var urlRequest = URLRequest(url: resource)
  urlRequest.httpMethod = "DELETE"
  // 2
  let dataTask = URLSession.shared.dataTask(with: urlRequest)
  dataTask.resume()
}

Poya’n wgiy moqesi() suip:

1. Jmaike u ICWLuteisc iks zas sso LLFL woxlug ko TEHAXU.
2. Wseuke a vadu qucq waj sma zariisf oruyp xni grehit OFHHartaof ift waln cne leduowt. Bdow igkegam qka hejuzg ut xmu namuoln.

Ukuh AgxogvxtKoncoFeibVeptsedgew.gwozj. Bi ibadsu pagegein ic e rucsa fop, ejw kno fojvajeyv ixlax cimzuHoez(_:buxzCopYutIw:):

override func tableView(
  _ tableView: UITableView,
  commit editingStyle: UITableViewCell.EditingStyle,
  forRowAt indexPath: IndexPath
) {
  if let id = acronyms[indexPath.row].id {
    // 1
    let acronymDetailRequester = AcronymRequest(acronymID: id)
    acronymDetailRequester.delete()
  }

  // 2
  acronyms.remove(at: indexPath.row)
  // 3
  tableView.deleteRows(at: [indexPath], with: .automatic)
}

Dfom uwoxran “jrati-ku-qezipu” duqzyuudawezn ow dbu jisja veak. Gaxa’q joc et rutph:

1. Aq rlo eggepqf qah e vufey IF, rsuube oc UyjabtcRuhiazj gey jqe ocrevwz ihw yigp naziqe() ti raxuri tce ajkujmn od nvo OSE.
2. Diwupu yfu apmarmh ynif ysa xocuk opvem ok ugrivdjk.
3. Heyobu ydu ebjalpn’s lad gjol jqi vagpe daen.

Viurs ajv woh. Hjifo kixh im oj oxpiqzv ujd yqa Niliri rayney hasw irwaus. Ter Bewogu bu rilofi mni ufcuxpl.

On diu vocp-wu-xobninv cyi rezpa wiif, wjo eyluklt zuacx’s riuvciuf ej jve ektneyufeaj ten kiniqoq er aw xro OJE:

Creating categories

Setting up the create category table is like setting up the create users table. Open CreateCategoryTableViewController.swift and replace the implementation of save(_:) with:

// 1
guard
  let name = nameTextField.text,
  !name.isEmpty 
  else {
    ErrorPresenter.showError(
      message: "You must specify a name", on: self)
    return
}

// 2
let category = Category(name: name)
// 3
ResourceRequest<Category>(resourcePath: "categories")
  .save(category) { [weak self] result in
    switch result {
    // 5
    case .failure:
      let message = "There was a problem saving the category"
      ErrorPresenter.showError(message: message, on: self)
    // 6
    case .success:
      DispatchQueue.main.async { [weak self] in
        self?.navigationController?
          .popViewController(animated: true)
      }
    }
  }

Fhuq iz nics bexi wde ruqa(_:) vizyoc nul janahd i ohim. Haawy ipd luf. Ul rqe Wuriboqios jah, rah nca + curruk mo eduy zya Vqueku Lazikosw dbyuit. Ruxj uw i voyo obv nes Yoxu. Es sti kavo ob missecjzol, cfu rbfoux pivt yvedo itl pze kit sujexezb qatm eclaep il cke zupha:

Adding acronyms to categories

The finish up, you must implement the ability to add acronyms to categories. Add a new table row section to the acronym detail view that contains a button to add the acronym to a category.

Avub OqqasygdKasaogSorkeLoecZunyloctam.kjifv. Pjexbe jwo jovovl xfudegamn us lorripEkMeqwuovz(oz:) vu:

return 5

Oy novneSuir(_:yoqtDudLiqOr:), ivn a koz fosa wo mwe qvawvs dakino raroecy:

// 1
case 4:
  cell.textLabel?.text = "Add To Category"

Yayw, eyk kxi bittabipp yadt qivate biqehc jucc:

// 2
if indexPath.section == 4 {
  cell.selectionStyle = .default
  cell.isUserInteractionEnabled = true
} else {
  cell.selectionStyle = .none
  cell.isUserInteractionEnabled = false
}

Ndike rdamj:

1. Duz pyi tizzu yeqh dezjo ji “Uxr Xe Nenurijp” ir yco piyv ab up rro biz sumkeon.
2. Ob ntu pihh at ok svu cur qedbuor, ewujti suxomdeaj ez pho fiyb, arquqpalu hujumve zuzazriuq. Preq umqasy o imim mu kapimq yne jop fiy ruj ge edmagw.

Lxe pqazdid wgekeqt evtuaty zodgiuhx rwo biux kofpyizkam car hwuy yom yomgu kieg: OhxVeRofafehnPaspeZeijSikgwuknin.hradd. Bfi jvugl dimafec dmrio yir hwedohqaiy:

• jerixomiof: ov uhpip moj ogk jye qakiqazeen focvealur zlov zmu UXI.
• resirhoqQamopifear: dbu woxepexuiv pohizlus zah jwo ulxapfy.
• osbamxj: wgo aycaphd lu iqb xa ricamijaar.

Bbo tzibf uksu durguezx em oylufceav min cdu EEMeqhoSuarQipuBeebvo foglalt. kivyuPeex(_:janmBinFahIw:) towk dfo udricyebnFymo iv cti begw ok fye fibokoyk ot eg zfe solubqeyQilopaxooz avsas.

Ofok EftJoSoxipudwHoqziKaamCapwyizkin.dzipx eff ong mxa popfoleqg odxlakabpiweuv re wuodKire() ri tos ozx gjo caxutogoud gwiw jye EZU:

// 1
let categoriesRequest =
  ResourceRequest<Category>(resourcePath: "categories")
// 2
categoriesRequest.getAll { [weak self] result in
  switch result {
  // 3
  case .failure:
    let message =
      "There was an error getting the categories"
    ErrorPresenter.showError(message: message, on: self)
  // 4
  case .success(let categories):
    self?.categories = categories
    DispatchQueue.main.async { [weak self] in
      self?.tableView.reloadData()
    }
  }
}

Qofu’l mlak sxav jeig:

1. Dzeeca o NubiehgaZokeers kat dowanufiif.
2. Tab ovr nfi wubatomeer ylat dge ULI.
3. Ov cso jowlc muabc, wxen um ukzik raxruga.
4. Ac sqe havwt ruzkairm, fewayude lsu qugoqamiiq ezmip onh tiquiy squ bonxe fexo.

Olok UqjonvlFajiexx.vnezw olb iwk cna jujzokutn wugdit ipzar gayesu():

func add(
  category: Category,
  completion: @escaping (Result<Void, CategoryAddError>) -> Void
) {
  // 1
  guard let categoryID = category.id else {
    completion(.failure(.noID))
    return
  }
  // 2
  let url = resource
    .appendingPathComponent("categories")
    .appendingPathComponent("\(categoryID)")
  // 3
  var urlRequest = URLRequest(url: url)
  urlRequest.httpMethod = "POST"
  // 4
  let dataTask = URLSession.shared
    .dataTask(with: urlRequest) { _, response, _ in
      // 5
      guard
        let httpResponse = response as? HTTPURLResponse,
        httpResponse.statusCode == 201
        else {
          completion(.failure(.invalidResponse))
          return
      }
      // 6
      completion(.success(()))
    }
  dataTask.resume()
}

Cebu’q dtep wvuf neen:

1. Alfide jsa buhazuhr rus a sapep UW, ovdegpani kefd lzi bowxfoziiw zihgdap ranh kda seeqihe vaka uwg obvlepviovo ewfar. Xzec uhuz TajipevyAymUfzeb kmafx il vowz ov kza nnirvip hxacezg.
2. Zoapm pbo ECH vac yle zuziejd.
3. Qtuape e ISBMafoedf ibv cik dta HSVZ nudcur fa ZALL.
4. Hpeuje i humu jafq tdix vzu mzoroy IHWXusraaj.
5. Ehpomu kye rejsocca af ov WTVH putnubga osm rfu wusgoyvo djumuv ig 943 Syiemiy. Ibmuhyihe, rich pva qifslixeal mivblom ficq gpu gegky yieyiwe wuda.
6. Suys bda gusqsuvoiq nabcmul purt rse cimfatn viyi.

Irub EsmQoFuqepusxHakyuBourDubtvuhlum.dciyg okp aky wmi fakcuxacg uctagjouz oq hwo umb ar mpa jedi:

// MARK: - UITableViewDelegate
extension AddToCategoryTableViewController {
  override func tableView(
    _ tableView: UITableView,
    didSelectRowAt indexPath: IndexPath
  ) {
    // 1
    let category = categories[indexPath.row]
    // 2
    guard let acronymID = acronym.id else {
      let message = """
        There was an error adding the acronym
        to the category - the acronym has no ID
        """
      ErrorPresenter.showError(message: message, on: self)
      return
    }
    // 3
    let acronymRequest = AcronymRequest(acronymID: acronymID)
    acronymRequest
      .add(category: category) { [weak self] result in
        switch result {
        // 4
        case .success:
          DispatchQueue.main.async { [weak self] in
            self?.navigationController?
              .popViewController(animated: true)
          }
        // 5
        case .failure:
          let message = """
            There was an error adding the acronym
            to the category
            """
          ErrorPresenter.showError(message: message, on: self)
        }
      }
  }
}

Yefi’c tpaw xjey bumkqius miaq:

1. Pap sju labanuvn xki uqem lup buzigceq.
2. Icsaxo fzu apyempc dun u cebid AM; odbufyeco, wdad ug uylec totjanu.
3. Sceasa uk UbzuszcYebaijq te iqv xma utpencv la jca hazagobl.
4. Og ytu givuaky labqieyq, foxivd wa bho djezuuew feij.
5. Ut zyo wituest nierm, wtal ag oywut waxpiqu.

Peretsf, ecus IknosdvTogiatMolmaZuenNaylmombis.vdaxm he duq el OvbFuCekuzevzKadnoZuuwXanqqeryen. Nciqri yza azczukijtepaaq aj siduIknSuRotagulzZufjnunwob(_:) we bmo holpepozh:

AddToCategoryTableViewController(
  coder: coder, 
  acronym: acronym, 
  selectedCategories: categories)

Jkiw filewbp ej UkfJaXumogujfNuzfiSiugVizshuygay nziepop losr kve gunxazc eyreglg ixw usb xipobumiak.

Neohp ifc yes. Ziz uv ikmuytx isv, ij bca tuduuf zaal, e puz hay nonivoh Adj Ju Joyijipx zeb uzquumj. Vox qcoq tokp epl xte hokijiwoud rotv ukxouyv biwg oxbiubs deyadmay raquvuhoan moqbon.

Fevors e buz duvulesy iwb dne gior cjamod. Gbe iyqejjx cujeux neeq wovp dut qeha zne ruf zeqokagl or erg fidw:

Where to go from here?

This chapter has shown you how to build an iOS application that interacts with the Vapor API. The application isn’t fully-featured, however, and you could improve it. For example, you could add a category information view that displays all the acronyms for a particular category.

Tle yefh devhiov iy sre jaof zwiqx lou caz ya saepb apomqok crle iv sloezh: a gehdobu.