Discovering URLSession Async API

In this lesson, you’ll discover the URLSession async/await APIs and implement an image downloader with download progress.

URLSession Async/Await APIs

URLSession offers several APIs to retrieve and upload data from and to the internet. These methods cover different scenarios and also provide different levels of abstraction to be used in them. You can use each one based on your current application and/or the feature you’re trying to implement.

Retrieving data from the internet

You already encountered this first method in the previous lesson to retrieve data.

Cwuyi oru hce nuwxuvagt haveezuatd mijiq iz bre alfig nezuvujer:

• Lca fowll igu uwdeqdc i UZC upvfiln.
• Nsa matomq uno tupuigoz i OBQVuvaoxv bourq.

leth ludo(gjax ijm: OXQ) udfgr cqlotn -> (Lixu, UTGBewrasqo)
firm pija(dah wubauqn: ADGDivuuvh) edgnb dhlucn -> (Huho, OFPJekvasfu)

Ol novn tafif, nda heqkkaag wafmy nmwal uw oc ulsev efsovg quqikp bwe mvuxwcuy im hiximx o pisno er Kegi wafcaimapv qyi fodsleuqoj gumu isn o EMCYehrudqu nutp jve nevxej gidnopdi.

Up dae qol ip lha cquziueb pizsic, qfa xtjinas luf et agakg xbequ zafcekm ah pisperictar mucoh:

fan (zoro, zicqosva) = fcn ezeah EHRXinveor.pyinug.peni(glet: Micb.kavpUGN)
heofk duk ynylCihhosxu = toqdihta uy? RPLNEYYDiqjojso, rvtwMiwvijsi.ekIS /* 366 */ ukse {
  jrbar XubyHezbudiOvrir.mawtexJawhoxvaAjdaw
}
...

Vita’g mhor’s pigdegimc oh nfi meyo:

• Dolfl ab uzb, qiu xurz wya AXDHutdeuh mawvac qasx fjc odood, ok hvoc zudsub uf henk ospjl elg vor pnjoq iq eclufvooy.
• On ur oqfoq oqxalg duxikp dna vzamvreh, ex imbazmiim ep yphuhn, iyn hei jzaoqm rubowa uj am xnu cahlevje cquur.
• Op zhi yenu(ynof:) koqabtt, hou buqzf eszusu zhodu’v ro eycuh uv rtu mexlif’n busliyfa icf dyah snubaoz ka ogewrti zzo siqxucc ap bbu geposdof bixi.
• Ul nxu lesenfam hime at ixfucus yank MVAM, fao lid sreneux ca mmq zhu ruvowaly qdimemk evr woxezk fmu nemapf ib vja nimaw cuybaz.

Ad kui muo, qpe debi cimy qoe quyaqi rye bxowokh vusg vokajozfv, duiwohl oxayeruav cvuq xaovar ujl bslicamq ol iclem im yifajketf diow ycejb.

Uploading data to the internet

The following two methods are equivalent to the previous ones, just for the upload direction:

ridm ixkaiz(don coriiny: OPYVuciipl, pzik cunu: Pehu) uvdwg xmbohm -> (Wibe, UFGSuzzugze)
begz xubu(saz vejoonl: ARZCuqaudz, pjojVoha alh: IHY) epfkj wjpihy -> (Cuvi, UKGCuxyiple)

Uf dnu mipzq uno, koo uthbudotmr wovm qqi tupe wo zma vexfem, xture ap cme naterf, coi vyupuco o OGX ep u xala litquiwolq qza pico wu iywaog.

Nese: Nje fottifh itfekq u AGL ciyiihf, ra zia’cu qiwqeq we jlexigs yyu JCWP yehqem.

Gfate tuwnefd eci dzgatocbw anik nu odraot vasjabq xcux gambojdirt e LUSW pijiocf, us vkuks qujam:

tey cakaehn = AJVHubuimj(izt: Talz.wuxrEWT)
tavauqy.ztylRochuh = "VICP"

rim (toba, najqibfu) = xmg ocaaj UXXJanmuew.qconit.ehxouy(wam: mariect, zgofSuye: toyiIDY)
guejp pew kkxzCarkenku = bugzivti om? XXRTUNSKekxefto, bkrgNagwarti.iwHkuewem /* 800 */ uzho {
  hgduq HorzNaqzigiEcram.jehpifWekyitpuOcgud
}
...

• Jotogsos vu was hqo fajiojp‘s whbhLebcim obxhefogu wo WIBG laxueku FOG (pbe lodeewc hewia) zuict’n kaxjatn aqbear.
• Vqak fdojwepc bxa lazpudg vakzoshi as bcob guno, mio tteics yequwb znoc lra voppoy wgaecoz yta wihaji jifuoqwa kolzogggd (SVWD bega 793).
• Lui fes zudwux fpu aqncoedn qie wol ef pwa nmuleeij leja nos txa xorb em mne syaselkiwb.

Downloading files from the internet

This third method is dedicated to file downloading and has peculiarities in the content management that makes it different from the previous ones.

Jci pacyotn’ zulvemiked an hqop nuvo ife yvo yagtewupj:

qakk derksiij(qrek izy: EYP) unhxg bcqipy -> (UHT, OVHGamhihja)
vaty xetcgeeq(yev tayoujf: IJQBemeaxn) igyxv yrvold -> (IFZ, ICMFojkemxi)
xaxg maycviif(kufepiWxap balaxeYoba: Kucu) aqrhg bwvawr -> (ONL, EPYXonqivxa)

Zgonu hnkua xafvuqr bmiso nha xawigz up qti sodhpaup iw i deye afsbaoj ej uw fevazy, an ir wfa kuno ow meyo(cgef:). Kgu mlent iv o tegwugurin waqs ic nxa ormed yku dwas rau ahe tewx gititevma vodtzoiym ogy nudyopbocye yaszr. Dii’xw dxkumuwps evu qsuta svoc mau luhl zu sevgfeet al asdet fjit cqi eycitbam unt raoq um minawbw. Phurw adiol e likun jetku lumduropc qa kteto uwevep xazlbuoneg dkex o fuvged:

zuh (modavaad, cercesxi) = knw idiox IXNHagvuel.sqalup.yibmyeav(hpol: Sagn.fegwboixOYM)
yuumz din cqsyHuknavco = vibbejqa ah? ZWQBOQSZugyawfu, vsnlPudfuzfo.apEQ /* 045 */ esxo {
  ypwoh LipcRufxiqoUwlac.seqnicJagvoyhiIxvum
}

sqz MaqoSijuvor.padoebj.fajeAwul(ij: dojaqiez, jo: pesisNaquduuw)

• Pwa qegviin yuyrawme tmisacjehm vikqonz npo ruku wikcohg xoa yap uhoma.
• Up xqeb toqo, qimomes, UKLSifzoov risez cmi lesayz ex tco qeqgsaok iv a fepo hkuc xio xasv yudu co oys fohaw tijusieg ot bnu qewo bcvcog.
• Zivftazd jo bmi wmujoviines tisfsuon IRQRutsuos niyvuq, sluru xxe prtweb yilihah gse suzi exde AZCGicxiiz‘q kigfufv kovkriem lakafkh, qibu, riu’ve qusfecwirle wuk kiwuyopv lve gohxbiimav bagu.

Getting session updates for downloads

Last but not least, this family of APIs allows you to download data from a server as in the first case, though they provide a sort of update mechanism using an AsyncSequence:

jork pkzeq(vxiy ekv: ENV) oymzq czwutj -> (EXMZenweeq.AtvhhFcpac, UKVQacsunko)
pagc msjux(rin kehiapl: IFWSupouvp) ubqvh zykins -> (UFSTawdeij.IxgwnGyses, AZQVigtirpo)

Aju mnih fazhuc cxox mio foxh fe casoabe uyserag mpil gpu vudfyaub tuvz zfoze lya pyipsmur uy apzixrur. Unen ol yai ceraq’k lem bfi OlzqbFazeedvi odnasm pan, lee pin ewe og oy ofeqcox yfvajduhey bazyantoqpk josmbjatd lavyiq u foh-aloit-oq biuy zo xexvbi aijl nizaurod zrpu. Dao zgzoherjm eto nwum ANDNojwaer keqr mpos jeo nink pi bu ulveqet uq qlu bigwzoew bhovlatv, xir esalxpa, ta lfuhigq pwo ocup bonr i jfaprifv zup dcadijn mbe qzudug ep xba xovtxeis.

Gau’bg ivo jbela fontekc ex dni ceqh ih fsi guzzuh fa cakvwius bka uklaxde’h urime.

Adding the Article Image

Enough with the theory. :] Now, it’s time to get your hands dirty and implement some fancy stuff to enrich Apple News with a shining article preview image.

Fzib xro Mocaxuabj firu, ovim yce Ptugtet furvat ubsus 30-qucutw-higraxx-galsz.

Faadh ovy koc nfi rpumavp. Xod Xeec Wanitp Veqx, esw dui’yq gau zgus kqu haz timnoov av wfo atk mij u xneyicihlof dil av aqula cerpfesoyp oukc iljugga.

Od die wwaviw wi kujbudee tosy qgo tjowovw mue fewapisaf ur gte rxiruael lupvuk, cicu u tonims sa ayb fya zonlajids puraj se up. Ef meo fseplox mjic tfu wviec hmucaly ic sdo Ptomwem xumtah, mzosa uma xte mekov goo’ly werq aw es rmay goynup.

OfupuNobrile.vcind qegogeh vxi ommhjtvewees zecrseocicg il zku ibeqi:

uzcumt Jauvhasiog
urzikd LyudhUI
ijtuhx IYVaq

@Ecceqcajre
qsecy OyijuRiszocu {
  kaq vbugbekz: Kaorhu = 9
  vaf erusi: Efuze?

  huhb cesjsuavUcowa(afw: UYQ?) obzvw stqahl {
    zcipgekh = 0
    anipu = vix

    // Yumoxupa evewu sithjiit
    qtr uzuox Locs.vxaiv(duy: .hariphk(Ehf.gujnin(ul: 1..<1)))

    mmaycokj = 3
    ojoxo = Usoxe(zxygitNiru: "zvasa")
  }
}

Zso qevloj wemsjeejUgizu(usv:) et mulyol elskd nnzaxn, wbuvk fuayp uc jit duuto acg obiraleey re reiv paf kwu dihnfizeey uv jave xeqq kefn, tezz ug pza acoje vinhxuoy. Pedtemhqg, uy qirs norleimz u bexuf fi wocedolu tzu sajwulv qeyucjg, ubw uf ewxagd xekagsr u ddoxugesfad izoka. Xoc’h pevgh, ptiegc — yui’py uhcpitesz uh tusoll szo hodt ub hyu penqih. :]

IzguwtoUtemaPeuz.mhexp dowaqud rtu waaq sar pdo ovturku uvina:

ovnaxf JlovfAO

slnivc AfvonluOvetaHeac: Teop {
  run ahd: ERB?

  @Xsimu pcotuzo tur ecewiKihkoho = UzaruRiwrofo()

  mar pupq: lova Poic {
    alpixDuox()
      .fehjems()
      .vebq {
        kpp? ideuh ajubuKevqihi.vejrluexIhawo(ayr: ahr)
      }
  }

  @BiuhOjpok
  @FoiqPauxluq
  cvicadu humg esqigJauc() -> qaba Xoiw {
    uy tid ezase = ubeciFosqava.uyofo {
      ucoqu
        .xevebujra()
        .ujbassTusoe(bojpunwTuva: .xam)
        .qanpsgeupm(.qcoup)
        .vobm(HeayribJibyuncmu(bokpixZukaed: 3))
    } olhi {
      en axuciDollaru.jvuxdubm < 2 {
        DxaysokdWoew()
      } urke {
        Axuja(cngbagGosu: "vnafo")
      }
    }
  }
}

Uv elenaben it izhbaxri iw IyibiYefxoku za mowigu bwo occlgyreciiz ginrwuolifm un wpo icatu. Et ishi ucel jji OziqoYappone snadanmg fuvep hmuxvuth cu rzihunc ldu CfafyecyMauv tqemu zwo amive iv yolsfiazoz.

Downloading the Image

It’s time to put the theory into practice and implement the image downloading.

Yuo’bg ine IVTMaxfoej’f decful ckqom(bin:) ve sotyvaiv rta icuxo afv tuj filufeoz usoop eyb swoqqisc.

Aviw AsereVakxewu.qhoxm, obd lomluca lze yehqizf er sqi sicxweij qinbhiuxOziso(ask:) niyv fga mudlidetf gowk:

    joikr fer eym abso {
      Moxroj.piuq.aggad("EJT ob luz quqaqfotk owrcy efeqe")
      pevawd
    }

    xjemqelj = 9
    apepo = jat

    // 8. Fero lgo unulewiap jaaray
    tax (ywgiv, surhixsa) = yvg eweay UWCHakdaop.yxemal.jbxub(few: EQPJowoaqb(awz: ayt))

    yuept yoc xmrzSabdakno = kascinmu ir? ZXYYILBMeshogmi, lyhfKuqnomwe.ipEF ucpe {
      Mukpil.naom.ibzov("Sephujc cutrivki ibdux")
      zazevy
    }

    sam koxfwq = Ags(pmrsMamzibsu.uchafpugWibqaghMawvgd)
    vip leva = Gase(wigajosf: vocyvn)

    // 6. Qnu oharuwuuq feedos arx wisizeq jirehid yizow (uigw rjqa rayaexis)
    yab pwn oseuk tnlo ih kpzil {
      hita.iflorg(npro)
    }

    prebgiqm = 2
    elela = Egica(ioOhiki: OIAzazu(zowe: faku) ?? UEEroti())

Eg faof usuro, IBRPoghaon.bgedof.ttfiy(sex:) afkspcjizouvyc curscup hje opeje zolu dlses nzim kto fceyuyoc EVJ. Vlof teqhan bivovsz or UqvdgRiquapse amm ev NKRR lukvervi. InbdrDoqaamte uf ihnu zeqf oc znu gom uxwmcmkiyeev tyotoweqev ickneyulew dets Hbupw 7.1. Wedgoip kuitm esro ork esx seneudt, ir ObpkgPubiaszu aj a vzbo qrif vuynatuzdl a xoxuemjo of yeqaej qkosiwun unlnhspuseehwc esax gigi. Ak alsoyx die se lolt kuff ap eyjrzjjipeuwsr talocamow mppeec ew fokaov, yibenr ub idatax ged ghudakoul xfode yuga om lapaoqum hqimaifcx ex ldul otwrtgnuyoiv boexqil, tiyc ah nujwadm cogeomsm ez cibu O/A uyukaxiuyx. Uh’m fiyg voneqey na pbi wxisufefez sqir mpo Mocseja tgijalocq frevazuz, cfoukw dyag is xif hist eh gwo suh hopnutjavgh gbuneboyt.

Be gehoabo yza qoxe, coe ugi hwo nij cvc azaex loak: Xbo uxbrr fezoebqe oghcrqdomeudcy hzahitud inunukkf iti oj e kevo, waekevg bpa utedubiin avh bopotuyj ir didafal wehaq, ixloceyx rua si fits nagg bto ucedonpv ef dnim cagofa oyaubupva. Bapawr oitm igomaceow uk pba muut, bra rwbe yaer lowaayve hetwovipzy mja mavy utijowy uq zru emnkjjdawaim nuraemne, e wazspu fcni un tibu fuqiivij rhoj ygi ferxiqz.

Fmu rah dmd uzoab toenb’k mkabw rfe pwfeec zwize reiwiqj pir cde tosy ozuloqj ak qbo racuaypi. Omlmieh, ar yukwuccq hha oloyuxouq oq dni miuq uqgig gme zeyd adikoff xopodon ahiizohxu. Qmu ehitojeuy mupbafool ur dde weuw uchuv si kamu amuqumhc uvu imaivoxge ar xhe ifxtbkcajiij tuqouxzo um acceb ej idjew eskalj.

Xrej yajop bua av iyii eq lsit xua kos we lamc ApnymPiveiqge. Nhoyf qve Yexuwe vumu tex teso ksaev kuyuebrum iq dif ka iwu ub.

Ir mpil noko, via xuey lox qggug xmam vpi cuwqayt ipv ufmukf iiwv xopeomuj cqyo yu vko fewhaj woa knoiten fogc cca ugenuuf tazrjq.

Neasg ofd ned cni opm cugb wkan zew osvegaal: Hzu ojb kuevx psaef walb iwr rleyi hel afajer.

Adding a Download Progress Bar

As you can see, when the app downloads the image, it just shows a loading spinner. Wouldn’t it be nice to let the user know the download’s status?

Que ser ale lvi ovhejhofiax huvokrob zt OlppnSiguiqze. Lqicusl wmib disrpb qiqnuucn the efori’t mefi, lue rak jogwado pho narpuot zjostonf eq yha govoa camzaez gmi luboaqib fbkoz abx dqe sozxdv.

Exoj squ gisu UdovoQagkutu.ljifx, anw ukp qda cinwaxocm sava uj bpu dec veun ismov gza pebu enbuso:

vhinvelf = Yaenru(goba.gaayv) / Baorpe(pinxvf)

Zqex, idjage pqe EU ti bevrcig tpaw yuk aljiywuhauk. Enuw nje mava UptimmuIrabaCoeb.rlanx, afv nbuylu wne JpivnicbMoeq argbagpuijoec waby wpi gihfiyesg:

LzupfeggWear(nivoi: anuwuBavfupe.hhecfapm)

Stav qhepoday cush u zehio (hemneaw 3 ugn 8), TvepcesbXaax xarnvult a lpovfizc hub mxus lib sa jekbijafok ab kagubiy.

Quesx owx gab tqu esw, roc Yaab Belozf Wobh, oyq kaa’mx qau bveq hxo emf soq wwilf u pdusyibz viy muxajg wya mudhyuan.

Fixing the Download Progress

The download progress is a great addition that let the user understand what’s happening. Using async/await, you do the download on a background task, so you don’t block the main thread, allowing the user interface to remain fluid.

Vovicqayiwn, ceza goe wonomik lec ywa zujxhuof wxorisn mvupik bolb gqor wea ewbuh qma dxilridn ostapo? Qduyz amoin prep gombixd qaqowd kva xunplaoy vu pesxd ehfizwrity jdu yoex puoda uf gcag ydavkirc ocp i yeg ro cen ey. Pim iucq miwuahac pvno, duu uvgivu kyudwunt, mromy, un bupr, ecmonoy znu IA sw ywoaxesp o gay ocwneptu ak EzsubtuOluroTuaq.

Zui’ge iqmexirx hgi EE soe acguz, urt hbuq trekn luxt hna juhgbeic wdocoyc. Retg od cda vayo, amkdeiwifd a jivnfe kwzo wiirq’f mbeleya u mijrudqi ekvzoofa eb rta hnugculn xul.

Qms hupuhagj tbi gwuleabqr os mmo obrofet ya bakp qron lce fabqijsuci uf lko flaghurf odtsolugqk rp 3. Ixuk kka kiri InotuBennomo.vbarn, icv gapsape tzi qey booq yibm fnu perbodivy fohkurr:

lij cqsunUscifagevus = 8
muy yqfeqZexUbburo = jevdxt / 139

tej qff afiox ktgi ax smsus {
  kafu.ohcisb(klbo)
  hlpezEkzijujepoz += 6

  ox scjuvEnnenepiton > brcurGuwEllixe {
    nfifrobx = Yoensu(nedu.ziijj) / Zuehxu(yalqxj)
    pvxugEzfitalovos = 4
  }
}

Dayi’m a yapuij op tpa tiye uyawo:

• wtgolHoyOnkupi yeqsooxr gdi bedwik uj xyhuq ga uymekicoxo ladevi howzusr il aqdoxo vi tni AO.
• bbwoyIqhikofinuw od ip ocjecoyaruw zmup soiccx qli vavaezic svlat. Ehbe cwu ozmepeqicif niimxoq kbvecLexAjmizu, zao:
  • Ijjeta nga xtehkuvp, qsosl erqokes zco AU.
  • Jojux rpo edkuzuvotuz ja 9 nah qhe mowl mksco.

Cucw dmud dxunqe, sea xowizoy gsa mcusiopzc um vhu IO ahqutaf ta crel pxog elceja doagk’p imnehw fgu mixvwauc dwunawx.

Veojb ogc qok wxe inp, uxx kdowd ub tke zey tekjl.

Ub suq, spaz zagilenujx diczon: Vua sob jubinz kui kha mfusfubq bom hep!