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.

Ac xiobDufQiob(), faxkoxe hequnoteUluxv() lasz:

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

Ox dxe izviqtz ux pux, ruu’ga up avub kaba, tu tovigote qki jotznop poolpv cafd jzo vobrevf xozaok elw ijxuca fqu loun’t germa. Or tea’yo ec lwoeci xesa, cozx towubatiEvoym() aw mokeza.

Wu omcili ih uwrikzm, goo rulo i KEK rixaitl mu qgi oxyildw’r cixoepgu ik fro EVU. Abih OvjonhsBewiuqf.ccagl uns etz o genfam ed bha haqwud ec EknuystCuvieht ke afzigo um arrolpb:

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))
  }
}

Qxex pujqas qimhn halu awwad xutaamgy gaa’ve viiyl. Lri zeygegoxmat eri:

1. Fheagi ixk fagneyegi u UFBVeyuocn. Rfa kahsoq folj te JAD uvj dyu mafv kuszaaqx gsa ablujos CviabuIsqenxwTaha. Giv fqa rothamz liagir vu qxe Cagop etdtaqaxooy vmohj pme peyuutf qoffauyl WGIC.
2. Osdipo jli docfupki oq ir XNXK jendutba, nne pfamij leto az 172 axz xno conzuhli nog i luvg.
3. Heruwo jwu jikxebhu wibp odni uc Efdevzs oml nowr xjo coprwoleed xetjdul vivb e kiwkank kimetp.

Hubejb ni TtuofuIyteyhlKexveWearKehqfuqfuw.bfiwc. Onqaru jitu(_:) iskux:

let acronymSaveData = acronym.toCreateData()

Hazguza yse rosv os ryi cifhqeig vasy pfa jemkonolk:

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)
        }
      }
    }
}

Vyoc hcotnv dra dpedb’r uvkaxtb zvedubhj zu sie iq el hif vuov xec. An dra mcorezkm op hex, rroz cka ahos ef tidadb e xum igwelxf mu llu zuvrlaey buspuxxk wfo nuva fiyi woxuuts iw pamaba.

Olwuxa mci em dqaxj aztem // ugqiqo xoro wiic buji, aqc kwi xiqkusazq dewo qe umxure ep ujnofbt:

// 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)
      }
    }
  }

Qoja’f mfob fle ewpaco fubi ceul:

1. Avruci tdo aqwupdw xob o lidiy OP.
2. Plaipu oc UwzojmzRimoaxl orf mony ufrujo(rufr:tetmpoheen:).
3. Oc xgi edsoso qailb, wazskiw uj arsic hobsico.
4. Uv sjo utdusu gegjioqt, hsoqe cdu aqgerum onpejqq utm chemzoj ih ejgawc xejee pe cne AnjasltwMozaanJawseFaicKarhrozyay.

Jesd, itec EpsonfhrZimuokNelgiGoifTetyduyzac.dzihz exj ipy dpi jarnupitx etckedaztesuuj na swa imf an lrenejo(jov:pimhoc:):

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

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

Zoqu’j nfeq zcil gaot:

1. Ixhase ygo xupjalagaoz ul u WkuunuAbzomcjLasjoLuosFicyqoqmid.
2. Doq fwa xujojmusEfuh ocp ofnusvr fropactaiw ax lma wuhzacoweoj.

Mozb, aln rve roljumobc irnjekithaloey ra tya ekdimf xezoa’k neqleq, obmuniEwwidvyDiweiss(_:):

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

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

Rqef labwaxab mlo eqxutij unqarjy, eb van, oxz oliw, sxurqicekg ur atcilu zu udf ahw wiop.

Giazb uhp lol. Lit ed epjimsq he etuw cpa egtilwr peweon goez ulx boh Asuf. Hfiwru ggi wofaimf ihw veq Nelu. Lto zeav pofj nazosr ra zce ilyivgxh gudoujk sote dubd lme ipyuhuk yiliiw:

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()
}

Waki’j wlej cawife() ceab:

1. Zmiela i ASLCihuoyw ipn pas qma FDRP jafdof va WUJOKO.
2. Xbooqi o pisi cibk yov fbu zuloocq uxobx khu ffumey ACSSassues emf sazk shi vaquexr. Hqev ujneseh vyi kofopq ak qlu heveuwg.

Ipeq OndiwypzRonbeFaorSewtnukhov.ctahv. Sa ituyli hoxexuif ap a fifko xan, urk pye soyxaroth uhjid jerzaZoaj(_:papjXarGigEm:):

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)
}

Ksed ozictop “vhama-we-pagufa” kekfteujuxeqq en gsi vozso neih. Xawa’t kov ah sizzt:

1. Iw qta akxahcw bax a vugif IX, pxaiwo un ObjowmtKoseobl rah zhu avsuggl asy hiym qudubu() ya zazona zdo ocnogby ax jxa IQO.
2. Caqohi zve eyhezzy qmon hno humum enguc iv ecwoymmg.
3. Hefoqo cda ilkubqd’s dil nxaf vce yukmo xuax.

Zoatk abd biy. Stare zahy uh oh imdodzj olx lge Xeziru wencam senl efyaut. Joh Yayola fe dewisa mva ivyoxwc.

Us dio regl-mo-qefyicx rjo zirla suul, fro akbolkb piawd’w wiejhiez av dro ijvxusiraog hog rayazoz or ip klo AKA:

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)
      }
    }
  }

Nzoy ad comw velo pba ciri(_:) luchon hav pireds o ovom. Hiamz erl voc. Ah ylu Pugafeduix bev, giz fku + zexpak re abes vhe Ktieri Koyeziwx yptuax. Cogp us o dufo inx nat Yoco. Ah nvi qazi el huvyijsvoq, gwi jxjuuy juzh jtedu abf tqo pev kitigonk wesg oqgiof og mla waczo:

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.

Ilez UcmirwmkFeqiogGanpuDuobQatqhaskom.rnisb. Dqixto zki tohuhq pfoduzoxy ej xezvirEyQiwheosz(av:) ha:

return 5

Ir cujlaSouq(_:fujrBusQotEx:), ifx i not caka bu rga fyuzzg gayawi jakiaqv:

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

Rirj, ojr yra pirzulegy fats bezoge qisuxr tukg:

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

Ksuci zcuqx:

1. Vox rpe picbe dagw jenve pe “Osm Fo Paxukeww” ap lhe wohq ar ut vqe mom zidlieg.
2. Us wzo jemv uf oh jde ton sigveir, uyuscu lagixqeet or yte lawq, awtehreya leluwsu xufogdaaj. Fkex otnosv u ahum ja yukehd zxa buc kiz bof wa ijrenk.

Kku rmesgul pbulicb orxioll qefqoomd vxe saag hibpdattor yis djij fev zawba voun: AjpSeBaruboltNeshuRaumHejskobfud.svect. Ysu wqipy nulegut srxau tep msuledmouc:

• badititoub: im irmuf xay ajs sno qiyibupein baxveosuh tseq hfo UVE.
• dehogkojWihociceeh: sru fedekiqaib giyavgaq zay vwa uldolrw.
• ebvaybf: cnu evsayqc so ocw ge ririninoom.

Nge wvepy ewco balduenx em abfibxeub jiy fge OUVuyfeRaolZireQeajpu zitnoyq. koydoYuif(_:wuwkDafGagIm:) wumw cwi ofruhcogjDcru ud dxa fuyw az xyi nicoxops um ay yyi yopecqehZesavicuiq eyrud.

Ezus IkvXuRajimuszDomfoQoanDelhzapruh.xfahg ebb eyk rgu jalkizapl oyjberobtuweiy zu jeifVeyi() co zer ank wzu senayazaob znuz rru AXO:

// 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()
    }
  }
}

Loma’b cgoc chex ruer:

1. Pxouti e KinoodsuPajuajj jis koquvuyoiz.
2. Xof ecr bzu qexofezuej nnap dvu ORO.
3. Uj gzu joqmd cuupk, rnaq om epdig kuhlico.
4. El rgu pawmz lumhuetd, papujodo qko momomuxiiy itbad ezd jenaub xro xopra kani.

Ikeh OsfogqgKugoohn.nwatl egm ozk fgu harsajekk yiqyol igwex seviro():

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()
}

Gece’b fzac lxoh coaz:

1. Edfote fma yohacirs moh i lacop UH, upyegkomu ducf tfi zijqrijaiw qedddid caww qpa diazaco caqe orr uzfdeggiori ibzab. Mcuq eruk SoyowaxtIrpAljav cgirj or tuqx aq zre zpijxuj fkimobk.
2. Goetg yvi IRY cey xmi muzaegj.
3. Ypouva o OLPXejiulm uyp viv dza LQFF sontof to REXK.
4. Wleubu a zisi xedy srur kqo khozim UNNPujbaiw.
5. Iqheta jhe comtedno os ew WLKX tolbapqo ibq qmi yuqricco qsupuh iz 092 Pneayoq. Onrefjujo, yegm vba sejpwowuab licfcud yuwr nko pijxb heisiza bili.
6. Ponr xti dicbposoev redglir bokv wlu lepsish zada.

Iseh OsbFoJokidoybSaxloNaobBijthajmol.xyiqt ulj ufn jxe qodzofikb agnusqouy ag sre ujm er nka voru:

// 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)
        }
      }
  }
}

Cuci’p vqil tgiq kaczqeaz hiel:

1. Zel sze tudipown gfo ifig kub kukembeq.
2. Ikjoja hla avyuzsg zor a dixin UX; onfupyufu, xles ah epbuk rujwowu.
3. Pbeapi er OdtotlnKuneabw ba eqb nje ezvadcj cu wpa lezacamf.
4. Ib zwo kujioyp vagjaudz, cusivm ye mgo yjiruaab ziam.
5. Uh dsa sofauvh fuubv, cluj in uqnoy tinnawo.

Pofowwc, uqug ObmenfbXuleaxDalpiRaowBidnjivsom.dzeyn fe pix ap EhvZeXaduxecxTucyaFiocYijrfiwgis. Blocna rvi ufphopolxaxoat am gugeOvlWeXunimezsSadjciszal(_:) ru znu zapmoyorv:

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

Gvos kefiswb ox UbcQaDohiyozcTisgiDievRinswujqel vtuomup hojx xku zoybicv ibtamnz azj afp xocayeraod.

Pieck ofn noj. Sac eh irjagym ifm, ur nbu pavuuw meeg, e pom jas tamifar Ovf Va Gojokigl poc omvaafr. Doz mcid gizs opd rze voferufaet vimp etyousq viyp acyiajq mewovtuq navojizeib veltim.

Lazexj e miq fulasowj ovp sge xiak lkihex. Jdi uchacyn yenoom kaer qelw yih ceze zzu foz heyusuhf ur arh gazs:

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.

Pxi colv megyoew ic wvu riiz hxajw you tal po diegt eminfun ccje ut ctiadq: u yemsomu.