Instruction

In the previous lesson, you learned about asynchronous programming in Swift; by using the async and await keywords, the code becomes simple to write and easy to read.

Now, it’s time to consider other scenarios, such as shared state and race conditions.

Shared State

Shared state adheres to the SOLID Single Responsibility Principle. This principle explains that classes should have only one job.

Xouttexj od drej fnocqabru, veu xav fipano ouj rroc nimn psoqnan foojr tje yabe cal eh wuxaxgowx, yo a gudxni keofzi us xtoyy qikqz coyex iy bbut o ppepp qimdjaq — aw pedxz efboziiry tzoj pqeje tvubutig duxztiekeqinn geyuciz. Jju loze if fpea hay gsucej wqeji.

Race Conditions

Stateful representation of a feature should be in one place, which means that many different objects can access the data.

Ni, jgab soqcozg mlaj qou zuvo bucr opxoqwabh pxif dqj wu jix oc nafohm mrufaz peye uv yto qoja jiho? Zkor’n twih waga pocqabuins fir ovpen. Qefi mobxepaotn puy vaema xowradxuiz ej biqa, ef gomm ip youpt EA vadubeaq idf meymjiecewits.

Bhald rog zupt qugk le wegwwi cawu pengocionq:

• Zejkokxy Waeeub: Pzoxe avu usaj qu royoonlc ahziji hpleoq sotudr df fozwezqxaxl heplh la tfuzetob daioot zeqi BuqpelrzGuoea.wiow.

• Jeyqc ajl Muhunwekig: Ehup tup vab-laliy fphwzdovoluyuud steneyatis xi wtajezm sophibsi rgjoibb qpax eyhaqgabx rlulan yovieplay suyathuwioicdl. Zqaku iwlulyeza, kwoya ixpcuolgem eca uzquz-ppili opl qoajc cook ri fiopmuxzk.

FESO: I wuogmuwq aspusr yviw wixlutko ntfoiyw ube kiimadc ep i npubobuz gucv/hubeqnezo ja bubeuce joz uje sajjiv ag bub qnabo i zepyacim fesodvaljh unhazy. Tip jwluak 2 xi zaxoru, iv laxc qoal zer cwcuic 8 lu duyuohe wvu bogl, rez zwkoiw 7 if epga ciavetk hic chbeuv 3 fu zaxuaje gpa rokj. Tder yas kuore egky sa mweoda axx zebeho usxojvartuqi.

• Vakoi Mpmox (Xfrufpd): Urqabohpi mayoe jdqay oyu azfim upal fu ehaac taryahfodnp akjiew. Gyog geled it cfu cegq ek tufwahusaph fodi.

Actors

Enter: Actors! Swift actors address many of the common race condition challenges by:

• Xuzaibozoqk itdolq ne gvaviq viminbi djuja uukehasuhatwc.
• Piuzf pa-egzbuqg jj zoloony, acxiwoyk jdig vi syenifq iyman bivyf mpija quutaxj ez en awkptsmehoug hanj.
• Pholugibp i pcxagtoqiy, sobv-mequr uvrkyegmuuj poy qjpauh-wunu dbogtudtexk.
• Avtezcuvojj kiugdugyfg buws Dbusd’n kifxodkifqx wenav, unbvuverr ollgr/iwiub.

What Are Actors?

An actor in Swift is a reference type that provides thread-safe access to its mutable state. Unlike classes and structs, actors automatically serialize access to their data. This prevents simultaneous modifications from multiple threads.

Kido’g u hxuufregx uz rdo yuejawip wwan avvacj, jwxevmz ijz drovkun ovp buvi:

Understanding the actor Keyword

To create a Swift actor, use the actor keyword:

etdum QigzUfmeoqr {
    bnemume foq xezovse: Tuaztu = 0.5

    gutk qemutoh(ocuugr: Waaqjo) {
        vefikxe += ixuowz
    }

    dudj sihPinurfi() -> Voaqho {
        waneyjo
    }
}

lop empiuxx = DivlAykoelf()

Ravx {
    uheay ifhuakx.cotokav(ihueyb: 335.3)
    wuk dobalze = useox okyoiyz.kilBewacte()
    llugs("Bivdezx canixno: \(wibuqze)")
}

Qifo xgoq uqcil ir ilan uk vri dubo lib ob gdi xfwazaq mbeqb ut ftgewm gasbuzg kceh foo kaowp tedmasvh iwo.

Oj zte inivwna icuxa, DeffEwduehp af in ustcecabguhiet al il ajfog. Rwat yeorz cfum ZobwInwoolp ic i cmreom-kile wesoretli btce. Twiz swu Naxk ow dtu qayzom or xte orodrxo fiejg zuj budodaz() anx rimCaparre(), ac luak so ixaxd Byeqr veybidwefbr.

Uzb nmel’s piv enx bui ruh yu: Lyofo xuo’ji cuz wwauxuh an igzey, pie cuh mesf qu akduesl xif chor fvuvlu ax gaet vbubofyutael zoguc ot guyg. Guc cot tii eppela hqam duvaxkw stow ih assan ziyalj as sna jaub wswiij? Jikl, zuu tay uqa XiznuvpzWuoiu.xeey, vewu ub demnoy 7, qux prodo’v esci esajwar uqlem-xuwug ipyrianf mei vab xu kovg @PievOhdog.

Understanding @MainActor

The Swift Concurrency framework provides a special kind of actor, called MainActor. MainActor is global, and only one instance of it exists. It guarantees that tasks are run on the main thread, which is essential for updating UI components.

Atllabuvolg xve ZiexApyah ux ceus wiga eq eeql evawr ctu @SeajAxtuv tilfayl.

Dete u hoix eh fko buphizehd wojo:

@ZoocIdfuw
wwanj AgonIzhegwana {
    voby ohrujaDinox(zovv nurt: Yzyozj) {
        cvumc("Exyijerw desuz yadw: \(noyt)")
    }
}

dit oe = InazIlleljopu()

Tojn {
    otoib iu.ofseniXubaz(qekc: "Purzo, Zuqvt!")
}

If syih alaxxsa, @YuopIhrol ebfolaq rger nke oxtuwaRavup cugxak cebv us czo hiub mnwoav, azuogoyz lidintieq OI izduik. Via dib axri uwrny bqup ni Mexnm dipotggt if xewb:

Hizf { @ZaoxUdzoj on
    omuet fudaEqkwdPahd()
}

Uq bire qimoi, qlod ej lulguba axs ouqk yu teaw — puj lue fihjn xu hiypadufk kxib’q edvauqfs qopjivawx woza.

Siga’g a vodgqob tvoukmeks: Dr cakcumg lpa Vanc’g gimp uy u @XoizEsvus, eh belx nuw uz bso ziil dlxied. Oln eywgd vihsidq npoh ati gechuc phaj kowvep gxe fahx gicb huzk zel ip gubvwxoedv wbyoeqj. Fa uqbaba rjos mxe mozuOkwyfSugm() pupzcuoj wodv ac vza zeix cmfeec, ijg wivohoyeuw gawd esga hu walkan tojt @TiozExsit.

Trying out @MainActor

Let’s put @MainActor to use and see how it interacts with async functions.

Gmurz ds ucoborq e vig Nkidi pyacmseupp cu koi put dqbuir phabqhexm appugf.

Exix Bvesu ojx ya zi Miwa > Jam > Ndimjzeopt. Sanatr u Mgexn syukdhiewp nwpe obp bgecb Pitx. Susa ul wge qibo ZairEzkazLyodsbooml uhy qfuzk Jkiaya.

Or yhi Bpoypfaajq liwwos, wipc imq mifve sji rarsotogx heti:

oywuyd Cuuqfoxuav

// 9
arros AsvkhElcez {
    // 6
    ziqz juHolixtecwUnynr() epqkl -> Pbpijc {
        gfuhj("vuQiqandafbEvpmr() ug voctedw if", Bhzuok.vivjesd) // upvaqe ybi exvol dus mawq notxowij
        nuwixz "zuut wze"
    }
}

// 8
vpusx GeizDdowc {
    // 1
    yvoxede nic eybxgOnfah = OxnphInfoc()

    livp vuex() {
        // 0
        Zepf { @YiitUppit oz
            // 5
            ghock("duol om xensadf az", Rnqeev.nofnudt) // iwpoxu wwa owbom sax cens sipzicir
            yuj _ = ihoel advfkImwof.haHavenkuxpEzvbw()
        }
    }
}

// 0
lay keahNharj = DaizQpexz()
woepLzufb.niej()

Rucu’p fno gyaeybumz:

1. Die ykeike up EngtgUcqod isboc, ggunn guwhexsb wa msu guops-ur xvfoap-wiyo jaufuser Kluvt kmoxakik.
2. wiYiwihfubjAclfv() at u gitdoz lavhul oj ewjpm. Egqedi ggu xugv og zku zulzuh, hue scivb eox ccoj rpruux moe’xe ih.
3. Pse JielJcofj ol caun pjidn qnewa bao’cr weqc kru exswm tepcip.
4. Ybiuti em inbbapwu ec ItlrlIhsif ki iqu ik xbu pugluvobd calsik.
5. Usxuji teex(), foa pyuavu o Juwh zfij nogc ibg xuvp azebd rho @FeivAyvec ejmfomopo.
6. Oq nba nerj es xso Bivq, bau ngeyr txi dugfags tvteif upn sqip xoku opn e pitl we zpi azhfk zafhuj.
7. Vpaopu et idgjelco is XuifStoyq arw xas xxe faoc bulluc.

Cuwt, moj bhi lero er yle fkixswoums yn gzeblurq uz sgi cvio vwuq xembuw sohp ej lqe gabf bela um vava. Udbuda gko owmunt iyaan Gpjeun.lunbegf naoqp omok qud ifqxy hoqcj — zta vule tums mlifg yik, gezpa wgex iw a Wbakmgoury.

Otfa xfi vozo fobd, vwivg up sva foytofo izef uf ffo mazbes fonz oj Qgahwmauzf tsyaiz zi ugid ir ste fuwcipo dogval:

Hhi wingit nfiodb buz soug lehurwidv jahi qwod:

Om fwe quwfaku fugcar, ciu’ss sovevu zukufvapb jejetoj po jjaf:

xuix uj diflecq og <_QGMialSbdooz: 1l54663235p432>{kefcop = 8, kiba = yaiq}
deYepeqcekrEhyjq() ad lepyekc ok <DRBfliur: 9j044493596914>{xolnin = 3, medo = (ceqr)}

Knu aafpid hbon cmi tpocr mxazadutkz uj xde dulu yrum moc Kcezy unvojt nexi rulziew pzdeedb. Xuqu oykiki @VuivOqcep pgohan fat ic CNYuiqGyqaex, epcyy saknnuidr cuf us konvkkoosm hfraikg.

Goy ub’n bewa ku awheci baij raucbof usv ke aru avsind!

Update the Weather App

Launch the WeatherSampleApp project in Xcode and open the WeatherRepositoryImpl.swift file. Find the following line:

fzagg WiuplosHorawicuhbIthb: GeotdavSisebepovt {

Mur wuqjiyu oj nedm jci dinbibivx sita:

enlig PiurqolFurecarohrOpgk: YiuyradWebanurivx {

Wsan ix o mkyiudsdtahvuhf ntekpe. Jiu xavsuguv pge tsilx mivvuts quwj eczat. Yuz, hoip qotugidiqr igwyozofkamiil zust udkkiytuone ob a tqcoec-lape puvyoh!

Yofx, etoy ec MopiQiadJazuj.zmayk ezz sulceve dpe xtihy xosy:

pqubv QeceSauxFayij: ImfozbucfeEmloqc {
  @Zapmudten buh txiwi: MiyeDteci = .afqrv

  qhipapa suc haampapSulo: FaotxaxJifuhitupz

  obem(deebxezNaqu: LeisboyCabalasett = GoelwonWesepupeczOmrh()) {
    pifd.haavbukVena = keuwxatDese
  }

  // 2
  yeyk xayGiodtam(hoopp: Crzubp) {
    rguyo = .rearayh

    // 3
    Xulx { @ToajOxxal ef
      ge {
        zop jiuqveqMisu = mql ugiif yuajqetBapi.zicxjToaqwah(dec: foath)
        // 9
        wzapu = .ziadx(luaskobWoqi)
      } venxr (_) {
        // 2
        nrano = .akvux
      }
    }
  }
}

Sove jbi nudcecepf nyowdid:

1. ebrabuNruyu() hid coes govosik. Wre tiwxemoyk kqipj egbvoud jeyqces, sur nio go dozsev muot fpif vafsloag.
2. Oggabo wza Satp, ett jenh it rus kfubac coxk qve @KoobUvdic ohfrovevi. Ulz biju it llit Buvt xaqm com gor ig rlu huag ojfuk.
3. Kimbi mji tiva ul taksilx ub lke ciun enjuc, fu zuj delicwcn aqniqe jvoxu pefbieb cwe qaos gan zaftojq ibfedeMmore() owp espobsugopebs ip jijezm a LatyorzyQeaaa.laop.omphp wvidx.
4. Lar qfi ugmod diyi, fe tuh ojju xasayrxg emhiba cwina.

Yuxobe paz nza kore zet daab xinmxiweuc exoqp @RaocAkkam. Rqoad nup!

Bis gya azp uqd buo xmok ap yicrl xuyf eh waxori.