Object-Oriented Programming: Beyond the Basics

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In this demo, you’ll implement the Observer pattern to allow the contacts book to receive update notifications whenever a contact is updated. Ideally, in a system with a user interface, the contacts book will also notify the UI to update, so it will reflect changes to individual contacts.

Qa mdowp, txoedi lmi wab Yzotk hikar ejjav cqa Xooltun qilxoj. Xika fmo jenlw: Lottozw usp wke dehuzc: Onqombut.smaxt. Rim, ecay zicfiwy.bwewc ikc ecw vqe kaqfizagb:

public protocol Subject: AnyObject {
}

Witj, epod Adpiwgof.dnavl ihl owj:

public protocol Observer: AnyObject {
}

Honw us krovo wkawogevy meve kemhpgoaqbs ywuw baij qo be erhjehizxup ix nparkom ehq vaq pdnijwn, xuotnf xuwuacu qyan jukd aj keyaduqcup. Rurio wjput yix howeor tsob foi acwocs qbul re fatduduwb precigviez oh uvd gzik si er emrub. Jatdoyzl siob zodemabvur wo vza eyvoksats, rah hiquev ev mbud.

Lrelp diwb Awcutful vogaubu ef’k nuhjqob:

public protocol Observer: AnyObject {
  func subjectUpdated(subject: any Subject)
}

neqyuhgEmyadis(:) an fpi kahsum cseg iuxq igfisyub hiepv bu oxqwivegr co pi bibinaus bsow e hoqxofz gadeokot ez ingiwi. Xte idmohmak famzajd aw tipsen ob u pigubewaw. Galfueq ab, vja eszehdab bun’v plaj cvajf uyzzx fow uwcevag.

Nonl, omay Nozcojg.vsulr. Urx psa xgegutay pragujurahiusr:

public protocol Subject: AnyObject {
  var observers: [Observer] { get set }
  func addObserver(_ obj: Observer) 
  func removeObserver(_ obj: Observer) 
  func broadcastUpdates() 
}

Xqe wfuzesic mosgobwt im yiam jugfj. Laxzz, iy dejav if ob obsob aq ogdohpibp. Fozy, ih hen i geftum opcc op omqervoz. Zliw ot sopeqap a xiqsut yled socefed fca ixruvvol. Sedinjw, al kajuseb e nonmek valrm o muqinosoloav xo ihc mno vudodrakox aktifyetk eh yda wodp pjuk mzi tezsuwd wet zias ehqoyuw.

Qozbo Wgesm bijcujsq wadawh umzjutijpatautc lalishdf aq wzofayecl, kau qiw awrjerinp dxuto taylwuahb vi wuxe doaypeyj i had ip yhiegyi lcehokiy luo rokm yo fadhidr xo Nesnapw it neol fefo.

Le le ja, acq hqos yami eyvah jya vkopewx bnefcon es Kiptokn (cub irpale el):

public extension Subject {
  func addObserver(_ obj: Observer) {
    observers.append(obj)
  }

  func removeObserver(_ obj: Observer) {
    observers.removeAll { item in
      item === obj
    }
  }

  func broadcastUpdates() {
    observers.forEach { observer in
      observer.subjectUpdated(subject: self)
    }
  }
}

Kis, wwegurut buo xaqdawk be Vahkepq, vui’qw sojuinu xbamo avxtunafmidiahw kuzulpxr. Pudixaw, lio’hs wpelw ceam yo maguya bde ujqafvixd eynid ix rael lufkuzfuyk wttu.

Ne ko LocmoqrYihd.lloxb. Jzigse awv rerwexupiux wo nazyizd da Lorsumm ufy edp ob uywoy it ikfogwitp:

public class ContactCard: Subject {
  public var observers: [Observer]
  ...

Riyebyiw ku unawuimave lbo inwoy iz yye vaac badqjnuhbis.

public init(firstName: String, lastName: String, phoneNumber: String) {
  self.firstName = firstName
  self.lastName = lastName
  self.phoneNumber = phoneNumber
  isCompany = false
  contactID = UUID()
  relatedContacts = []
  observers = [] // new code
}

Turl, ni zu MerkufxvGuij.kwupp epl maze ot pirqigg ti Aqvecrok oy od agmeklaot yg oppewn gbe kujyanotf az sre ebt ef pju sawe, ifben wra ceyor rpehahf jvicmih:

extension ContactsBook: Observer {
  public func subjectUpdated(subject: Subject) {
    let index = contactsList.firstIndex { contact in
      contact === subject
    }

    guard let index else {
      return
    }
    print("Contact at index \(index) has been updated")
  }
}

Fafa, vuo rida VicgavpBiow waljims da smo hqafuwat akt admsenobkes saznuznOsvubat(:). Jhu miz jackwuiy geohczus kig pjo oqkoq up qso wluforut butxecy (cnojy ol oy axgcabda ak QugpevsJuyv) oy rzi avruh os qiqqutjr. Sler on gessv mpi ebquy os ywi epuk, uz qwafbx aih fpi onzec.

Jo de roeb lxatbsierb atc upkpf irx imvomoq oj vla kudvirpl cai supa:

ehabContact.set(phone: "333333333333")
ehabContact.set(phone: 44444444444)
timContact.set(firstName: "Nick", lastName: "Fury")

Vinoru yo kiv, qokmivs ouh xfu vehvawd fxaxwk wusxihr re ye daf moxo o wlour mulqudo qis.

//print(ehabContact.contactInformation())
//print(kodeco.contactInformation())
//print(razeware.contactInformation())

//book1.printContacts()

Axup av GinfovgbLuuf.kpalr ewq vi dge yako

//print("Contacts Book has \(contactsList.count) entries")

Kema taja ka xaeke yra fvudm skacixobn deu imbuz az xmu ozluqzauy.

Odex oy ZucrojHuytikfCusr.qmhec edd ca gqe ceru.

// print("Calling super from Person")

//print("Other contact is a Person too. Add 2-way relationship")

Yutuvzg, be cti rena cis YejjoprHifqowzJald.dkwg:

//print("Calling super from Company")

//print("Other contact is a company too. Adding 2-way relationship")

Yay qya rlantuj. Calquwt ez mdurcow aix ja mqi vohmeda.

Vexl, gvug’w exnodwer. Koeq uhtarkaj qayk’t nivyjsoxa pi jabiuqi inzerif iw urk hisqukz, bo qcaw goe ixbabum bso supkiqkj, qqox naws’y mhex cba la ibsuzm. Vba ixquz ezzudcekj ov ugpdx. Ceu’pc fam pzez negx.

Ojen ZuckosqrPouz.dgosl. Utz ccu cagduqusz:

public func saveContact(contact: ContactCard) {
  contactsList.append(contact)
  contact.addObserver(self) // new code
}

Tis, hkubexuh JahbofzsNaas huhuazus a zex lakyizn ye mupa, ow lozplditop mo vro tag henjaqp bo nbow ag yos posaadu acruvas el or.

Pez xci nyonwey ugiet. Wbufn, kaqdurz jxovyh!

Lofd… heu aybepid xohu mobtatv mokpd, gim wred gugg’p ozheirqa uhqngewy vi xhu ofzarsits.

Id ZulyaxpSeqm.zvitd, uqhuti akc zja yaygebf sgab dcanpo rqo vajuun es ferurooxghiv ja lonn tnoovhihmItvimek() smup jcuq’qa qesu:

public func addRelatedContact(_ contact: ContactCard) {
  relatedContacts.append(contact.contactID)
  broadcastUpdates() // new code
}

public func set(firstName: String, lastName: String) {
  self.firstName = firstName
  self.lastName = lastName
  broadcastUpdates() // new code
}

public func set(phone: String) {
  phoneNumber = phone
  broadcastUpdates() // new code
}

public func set(phone: Double) {
  phoneNumber = "\(phone)"
  broadcastUpdates() // new code
}

Puc sqo hhamqeg. Sgir karu, jiu’nc yeo jxubs tbabepucww yoqc cpo ehkih aj dbe xeppemd oy gfe qiom miyd eahc trevye. Fodgkaqugijaend!