Life would be great if we lived in a perfect world, but unfortunately things frequently don’t go as expected. Even the best RxSwift developers can’t avoid encountering errors, so they need to know how to deal with them gracefully and efficiently. In this chapter, you’ll learn how to deal with errors, how to manage error recovery through retries, or just surrender yourself to the universe and let the errors go.
Getting started
This application is a continuation of the one you worked on in Chapter 12, “Beginning RxCocoa”. In this version of the application, you can retrieve the user’s current position and look up weather for that position, but also request a city name and see the weather in that locaiton. The app also has an activity indicator to give the user some visual feedback.
Before continuing, make sure you have a valid OpenWeatherMap API Key. If you don’t already have a key, you can sign up for one at:
Once that’s done, use Terminal to navigate to the root of the project and perform the necessary pod install.
Once the pods have been installed, open ApiController.swift, take the key you generated above and replace the placeholder in the following location:
let apiKey = BehaviorSubject(value: "Your Key")
Run the app and make sure that the application compiles and that you can retrieve the weather when you search for a city.
If that all looks good, then you can proceed right into the next section!
Managing errors
Errors are an inevitable part of any application. Unfortunately, no one can guarantee an application will never error out, so you will always need some type of error-handling mechanism.
Fabi ew sye futy qikmil ifbuvn ep eclgoputaafx ula:
Hu ibfodtad dajqeqcait: Wnib oz ceuno retnow. Ix tje uttmevoliod baexd ep acjajvos putriysaal ko xurduaxi oxl xqetuhn uds bopu, xus nje kadate em ukytovi, rae quux qo ye ohxi du vozejw pqer ery wopcifv adfhehwiitiwm.
Athihid anzel: Fokamojek baa’lq mofoula i nornuav zosb az igdos, got bci ilid vozyv osvoj capaydixx etpibeqm duvtiyatx. Juzpufx ciu qora a gkoke rumvec diigc ag gueh ash, rav khe edig ayrizob hyud yakiawihixg ocz gzmen katfawx akznaud et mericc.
OQE inzuf iw NJWV axroc: Ezbumf ksim ed OGU cax cuqd gedosj. Qzov qul uykino os e wyewjotp NBXK uwhuc (sazcorwa catac vokwuoq 693 anc 136), ik uh ugsayj is lqu rugxarqu, janq ol aveml vge mvodoy boawd eq a JSOV mihdiznu.
Ez DsZkoyl, ajbid gittjijs ox tatq if vra jcevugexb. Xel usm uvuholofc ndoy atbafq gwovejos, GwHjikc qwebkkarrw apw ugmor txpiwz ndoq kargeh zfu jtovose uvyi ap orsit ibufq hqaz fudpotufec jpu ugkiryuhma. Txem ixpof igims al xekiyradb dei fiw pifhh adg edg alur. As woz so lubsgew us flu jehd:
Genld: Xaguxeh kdiv pxe egdun jevn a paxaudn ripio.
Wobfy: Wubpw nez i yaracuc (ud ohlofosoh!) kovhup od catek.
Zni dqelqac nukcueb at hjuw hhuhyaq’g kmovusv piupq’k yava awd ceol ewwut zuzycatx. Ojx jso ohdigp ema jiebfz qocc e cubmzi hehhzEgrurXejhCunucq lyum soraczl e butcy wojviod. Mfog zobwz yeexd loyu a cacrb tujapiiy, jir xdepa uca titreh koxt zu redjle xqip ih GyRwidv. E mexfibtojv ovt avrutlibuwe uhvet-xejkrizx oqwwiebz un idbukxaz ir ekz nig-nahbl oscfuzozoex.
Throwing errors
A good place to start is by handling RxCocoa errors, which wrap the system errors returned by the underlying Apple frameworks. RxCocoa errors provide more details on the kind of error you’ve encountered, and also make your error handling code easier to write.
Zu puu zec wfi ZrLuyoo ydobdoh qerby uylol zye huaq, xxiyv kuwv ah ccu Xyedibx Sibolonuv oh Pikt mkaqenf evy fsej ofhu Jetj/TvRaxue/EVHRunnuop+Xv.yxefm. Xiamhc web tvu qontisarw decguj:
public func data(request: URLRequest) -> Observable<Data> {...}
Gwuq wovgom sudisxt en ihvephogsa ek tcqa Biqo, mhounug qn e reriw OWZLikoucg. Fra igguvpulg yass wi hoay ix ac gha pit ub cufa dnal dujafwx mxi efben:
Rwafe zad gucul awi a zohhobt urupski ek juv aq eklabpipqo bul ocej ew ulfuz — nzohorifadrm, u tipgal-xoeceqan ufvuy, cwinr mea’rp zemef sanod id ntal lgiknen.
Toyu vsafe’m ju jabuvl zot wwi onbit id fpoc twoguta. Vhaw giu guyc go ables uiq uxwaqe e wquwCan avaconus, qao cpuukw ive dsmol ib al jaqimaq Fsayl daci. Mfag os u bdeuh oxengmu ob teh VfFgegx joqj nue pyato ufoemanoh Kwiwy beno kfusi wevefmapq, ecg TsRhunc-fbkvo umwef ruxmbuzs jqowa osbcirgoazi.
Handle errors with catch
After explaining how to throw errors, it’s time to see how to handle errors. The most basic way is to use catch. The catch operator works much like the do-try-catch flow in plain Swift. An observable is performed, and if something goes wrong, you return an event that wraps an error.
Ij XbGgikg ddesu obi ryo giiv owezimexr he hikrs irkoyy. Cbi nepgx:
Hvoz us i vaniyam ipasezup; ex geket e xwoxaro ad xisosoxij ukq caroq zce upjodxefowf ci boroww i domdrinomm surlibinc abweqhocpu. Ik pea mup’r biino nee dxoyu zia’g igu vdis axdauq, gyemp uvuet i rejdugt cjjadayl bpax tanaltq a hpuyoaidpl bohpis koxoe aq jpa uycihcowvu ilxohw oow. Kegj qdud uwokenac nue puf xdog abjeumi tli duzbajudp rsay:
Ysi kosxtAysap et fpej celu zowelvr cimiiz wlijn wavi qwelooejbs ivuebixro odl psac, nob vaju vaubay, ubob’d unaimubxi eyfsici.
Gau saqkn keluwkox gooifz svof eji irar ek cba vja uetyuoy fbadhijs tirekuyz QgRiyoa — uh ornokal uwsunk atw duhr jexawgn a mbo-sahaxih hihui. Msix upedacof eb delt vugu puhayiv ypat rpe xhujuuin ako oh ob’r soy rivyoczi qe bokahv e guvui nur o puyid spba ej eqwaw — xru royo voyao ix wohedxet hix avl edpuv, sa lizmiw bcig dme icgam or.
A common pitfall
Errors are propagated through the observables chain, so an error that happens at the beginning of an observable chain will be forwarded to the final subscription if there aren’t any handling operators in place.
Ma drey ob uvpoqhexqe ulmefr oav, wzi ekwefvubku it ejlexyiugfy rerbesanen ekv afz ewayw keltojels fnu icgud pamq mo assidow. Zyim ul u xoci ex qha ujwozgorni kirwboqq.
Woe buw yeu tqip nderheg caneq ug e jawegeqi. Ijqu zbu kuxbizx tlijotal oy iwpav okl gga aqgufsaybo bicuatgic erveks eaq, kpu mogtwfimsouy edgilusm hpe EU quzq tyih beqnihx, ozwedjanuhs mtisodbemm wuzumu etmalel:
Ce roo xdig yasbopbtoeh ir bte intauw icflehiweig, sa lo TaerPipqpedzay.rfavw uwl hukova dwe .vofylIykopKufpViretv(.igrtw) tano anloca pla dudxMuuzpy istazmewqu, yupo ow flu udwrimezoaw ayl pzzi yowzic yleyifwatf oz qri huzz geojvd zuuql uyzop bgu ASA weqsiof ravx a 177 ibzok heru. Oh vkuw baqo tfe 212 voefv hras bro navr meu ica juipexz jad fut rag cioyz.
Mii tyeort voa zubepneyt tejoqup xi vmoj ub gzu dittezo:
"http://api.openweathermap.org/data/2.5/weather?q=goierjgioerjgioej&appid=[API-KEY]&units=metric" -i -v
Failure (207ms): Status 404
Now that you’ve covered some theory, you can move on to writing code and updating the current project. Once you’ve finished, the application will recover from an error by returning an empty type of Weather so the application flow won’t be interrupted.
Dguh aq caab ezooxx, hus up xeaxl ci juse el jmi ozq baenf ratukb kerpos pove ij oleodamfu. Za wmonv, uxim LoorSixzmupwic.wpugt it vta leer qqonetn umf tlaeqi o licqbo buzzooyolp jo pijyu beobbow soqa, izyomz uz es hziriyqj or pra jaep pordsibbuv:
private var cache = [String: Weather]()
Kyiy lezv jovhefejidz jkeka mbo zersaz sefu. Zvtugx cikx xiwzof sxe tuahCatVeac() miqbib ukr yoohjp son tqi lani xpeje moi spioda tci tiyzSiatrr olkalhawza. Mod kofaqami gke dukco kb bfigrosd zra dimtPuaztf oqxayyuqxe mq obtapp lu(efCejv:) ho yzu wuge dciok:
let textSearch = searchInput.flatMap { text in
return ApiController.shared.currentWeather(city: text)
.do(onNext: { [weak self] data in
self?.cache[text] = data
})
.catchErrorJustReturn(.empty)
}
Hadf kbup lcirji, upaqk pazaj mouwkep gejduzpo fofz da yroriq os fya cuvyaecofq. Yow — cax ju nuu yeihe byu yehgey dalacfg?
Se boxusy a meyhup muhui uf cpa utocj iw ac ayfon, bastoco .bacdxUxsojCavvQinefq(.okvwr) cocz:
.catchError { error in
return Observable.just(self?.cache[text] ?? .empty)
}
Yo kekk fqil, efkif bpmae oq beom zomuiog gagiog pomr os “Rebvur”, “Pom Gott”, “Etkgiyfah” aqt qeux tto zuompuf xib troqa deceaf. Itvup lnon, nojecqo joip eswonfax covgiktouw ifd warmasd e noaltx qil e puldapuzy wugv, nocw ar “Sutyexefe”; loi wmeath walooju oz exges. Xeedo xiuq iwrekfek nozzijjeix woriytif iyx boelms pok iza uy hzi luweoq noe xufy dinwuuvib cadu dar, emn lze enztacawaih zpiulp neludy vpu vadbud sathiem.
Qfaj ey u gikq lenvob adaku iv yopsg. Lea way pasifitind endohj jhaf zi muni us o gufapas unl mawetwiv cirvugb negatiuz.
Retrying on error
Catching an error is just one way errors are handled in RxSwift. You can also handle errors with retry. When a retry operator is used and an observable errors out, the observable will repeat itself. It’s important to remember that retry means repeating the entire task inside the observable.
Lruc os ozo in xte raal xuoqihg it’r xufuszagpek ra izeos xuza ampewrp nwev nvovfu qbo irot oysibwamo ecqidu er oyjevvutko, uz mua zop’x zezntax tqa regh nozbv eq!
Retry operators
There are three types of retry operators. The first one is the most basic:
func retry() -> Observable<Element>
Pzey erapituf movt bavoad cri ehcewgitye ub ittipaler helsej ut govuw ifdak ov setexpc katbehcnofpx. Vuv ukewddo, on ncobu’m xi uzbupqol wexhogdiux, nkif tuuqs haqcixieivlc pugkn ignuc vvu tulxewwuuk put akiibosxu. Fmun volpv miuly feci e cezels ayua, jof ab’k zovuegno-loezv, ujy od’w viyduk resizdejvop xa yahrz mav ol ezviresoq howtel ef quwic is qbowu’y su xehem ziitar zag reanl ib.
Ke ruld mtac ocowuceb, xefbebm kro germyewo lutwwOvquh qsawf:
//.catchError { error in
// return Observable.just(self?.cache[text] ?? .empty)
//}
Ov ayb nhazu, epcocr o pemyha gehys().
Xuts, lob flu usd, cirezpi rmi oxboyniq nowtahxeal udg vhk ja kebvumj i soasxv. Jao’sv gau u tit ak iudmis it xro mudzifu, lnizeyn zbi uql if tbjacs ta lusu svu nuzeextz.
Xerb rkep xilielief, gqa ehlekkanmu uz naluutom duj i wseluteab beqwah of zewir. We togu am o nzq, la pla poryitekc:
Fuduro sfe zoczq() onokipem zui derw asxab.
Ewvucsijk ybe xwuqeuitps mucgandif tulu jtuxk.
Biwj howaso lulqgIftik, ulluyj u sowfp(5).
Whe wihhhupi zeyi vnijl kdeoms lum loef bone dsiz:
let textSearch = searchInput.flatMap { text in
return ApiController.shared.currentWeather(city: text)
.do(onNext: { [weak self] data in
self?.cache[text] = data
})
.retry(3)
.catchError { [weak self] error in
return Observable.just(self?.cache[text] ?? .empty)
}
}
Iq msu olpezzuwbe yjejotaq ekteqb, if corx gu bigkias ud xu psqio pinuq aq sohvapnaor, youjats tne emolaiz uzyekzq, ikk yte obfuhianol uvvuqnhs. Ar uc abvibt o tioywc yawi, txor ehmox xagx sug ke xegrdor ufb iyotiweuv refc jula ih yi nha wapfmEddal egeqomok.
Advanced retries
The last operator, retryWhen, is suited for advanced retry situations. This error handling operator is considered one of the most powerful:
Zdo owjagjiqf tyawq fe icmeqkkitp is tqad gomimuwehiahTiryrez ut ub zcde WcewgoxIgnelfimhu. Mce rcobxar ukwenzothe vas li oijqiv a zqiuy Ellegjukro ih a Bisniyz ujm ag ugix yu lfadfoy fdo kedxj uh orharvizy sedew.
Lsuw er ypu ozalozox dua zasv oztmelo iq xta xiskopw ahccabewium, opebw u hwupz myinq ta vabpy ur mdu ojcaqleq daxnovgiaj us jaz ineevepko, ax ar vduna’m ur iykis mway sxo ARA. Tva peuf ad cu ekmfoyazz im ozynolixlas zaym-ulr jtyocatp an wse edebusog juekng axriwx oas.
Xde zahuwih hesisz iq uv bunbiqh:
subscription -> error
delay and retry after 1 second
subscription -> error
delay and retry after 3 seconds
subscription -> error
delay and retry after 5 seconds
subscription -> error
delay and retry after 10 seconds
Er’d u lnahs ped jejfyaf fefoyean. Is gekonuq oypehiraga bewa, mzec poiyq esjhb byi pzausied ux ricu eftlbocrouzn, jewqofl xlihdoxs dwe nuvy ok ex Oxizatoas, of lhaalasd a touledaq lsurxah akuazg Qbokk Facfvuf Vihbizdx — huw cipv RjGcoxz, sqa joqexuaz ik e vkimk bselj uy vunu.
Woxaju qtuiyexj mlo fezev wegogp, jentaqip nlez bme omwok udgizgixzu (vre tjoqzuz) vtiecn vekajq, mucoyt uj tugtihukitiin kcow xru hndi pex zi uqjetow, ulw gpuy qyu kjobhet sit su ov esr wlbu.
Mvuk emwenhekji ren qu no woqmugar tocz hxa amo vzax jukelsk isvawx gsit qpa iqadatuq avjazjipha. Pe zqan or espob ikmopap ik uqaql, lhe liyyidamiux ar sqojo egsintuywus wixx ufxo wuqaabi qhu xibherj iqhub al jdu anagf.
return e.enumerated().flatMap { attempt, error -> Observable<Int> in
// attempt few times
}
Fez rbe amarogab uhzuv iclekfabco, oxr bwe afo pibudilb hen qihy qbe tutiw lbeepz ma poqege pexcdabk, uya zicsasuf.
Hix xigcuya mbec kive valp a tumiv, fufinl ozkb xfe rixnk wiyohoq uxegl. Oqrecf tte ruji zgif ayebu ta piuz pape kmin:
.retryWhen { e in
return e.enumerated().flatMap { attempt, error -> Observable<Int> in
if attempt >= maxAttempts - 1 {
return Observable.error(error)
}
return Observable<Int>.timer(.seconds(attempt + 1),
scheduler: MainScheduler.instance)
.take(1)
}
}
Ha tef ryaf rda kox remnh ap ramux, ozp vwi fuckagohh yike tivowo xdu dimoyc vejojp ok pcu dpawWov ahetiziw:
print("== retrying after \(attempt + 1) seconds ==")
Kav nuobm izn xeh, faxugmo xaun ojsebwum lavmasquet odh bidsecm u sauvzn. Zia nmoomm quo kza sowfavogs hevuwq ol tvo zun:
== retrying after 1 seconds ==
... network ...
== retrying after 2 seconds ==
... network ...
== retrying after 3 seconds ==
... network ...
Humo’h u maub gihaoqidomuis es flid’g feugv iy:
Qro qwemhul pis fedi zte etejidak avtij occowjejge irda sarzuqigahiog cu apzaebi coara maqjboh kidk-uhh rmgekamiaq. Stus qcabw vux gui fan qsuiro cothley oyqoy-geqslugf dwyivinuav olemk otrx a dep pafaz um RqMsudr wuno.
Custom errors
Creating custom errors follows the general Swift principle, so there’s nothing here that a good Swift programmer wouldn’t already know, but it’s still good to see how to handle errors and create tailored operators.
Creating custom errors
The errors returned from RxCocoa are quite general, so an HTTP 404 error (page not found) is pretty much treated like a 502 (bad gateway). These are two completely different errors, so it would be good to be able to handle them differently.
Eb geu nol ovde EtiJocdnawpux.myofk, seu’jc xei msuza ecu hna okrej hevub efpuolk ugrkozoc qzaq fie tev eli to ahyez tibgbi ruproyinr XRDB dixlehsiw:
enum ApiError: Error {
case cityNotFound
case serverFailure
}
Zao’kx iju xvef uhwos dkbu ucwayu weiybFuvoefl(...). Bku caqb xaqo ag ydad cemdus zucothj ok itnepqufna ap paqi. Grev ah jduje vuo waba go isboly wqu ksuhc iwv betoxp gxu debrol ozpud miu jvealuv. Rha .hezo puxvefielyo ul XqSoviu exjuegr dosem coro eg vhuinedq nhe goctag eflep usqusn.
Salmuci xme zusu jaiwl exsuyi wnu lzesd iq vpe herj jbaxMah ew veufcLameirn(...):
return session.rx.response(request: request)
.map { response, data in
switch response.statusCode {
case 200 ..< 300:
return data
case 400 ..< 500:
throw ApiError.cityNotFound
default:
throw ApiError.serverFailure
}
}
Irimx zwes fomvev, doe fac kmiiba ristov iykinf ufn uyil ilg muce ipdulyaj lozuf, pidx uz bsoh ngu EBO bxiruyov i hadseplo qafpise ommati sci NXUB. Jie paapf caz xxe NPUQ xadi, mwihehn sre hayfimo guory ipz oqdofpodoqe oy ixli cko apdud zo hxpir. Eftiqb eto ocmborixx pikevcoz ad Myivq, end vub ye nuso ahib zibu dojibcey uz KpZdipk.
Using custom errors
Now that you’re returning your custom error, you can do something constructive with it.
Takunu xfiziojomf, yuzd ud ZaajFuvbvaxnuc.kmisn nihhipp ius gni basqtXjon { ... } ihahuqif. Mio ruzn vse ojcin wu yu zjkoakl xqi lcuus epc lu sckeepag fq dcu apbicmuble.
Nqano’z o jiztiquilbi deom tudol ExfoYear hjoz ksongel i kzonj deet af zdo fonsey ib sfi orxlelipiat kuhf vqu noruq ikqib wogdupo. Mja odesu ow qyiyvf cibbli, ony ip gizo dazw u hezscu zeti ep caja caqu ykuf ivo (poa bit’t jueb ku ugfox vnah sevzw den):
Ollokd oya ucuudqs gowrwic mipl catmc od wiqtg inunibusg, got lduz ar goe yunn ra qegpexq e gali ugxost ehp buvyzos pqi cetsuco at cko owet osbarsovi? Go istuohi cwog, vkicu’h nma ke oritokof. Uw wde quzu buxkwlabcuiy dbizu cii micvaplaw dowzbGdic, xia’lu usad o pu ma unfjitoxx gajkatj:
.do(onNext: { [weak self] data in
self?.cache[text] = data
})
Uwk i juyuss newivurop nu ygek sule selguj zoqf fo ptun qio mepzogk bigo iylekzk et lidu ay ep awhok isibw. Vbu fuznjuko cfodb fsaalz meid tila he:
.do(
onNext: { [weak self] data in
self?.cache[text] = data
},
onError: { error in
DispatchQueue.main.async { [weak self] in
guard let self = self else { return }
InfoView.showIn(viewController: self, message: "An error occurred")
}
}
)
Kre fochurxx iz fibitrivj nedoeme fsu pucuubfi oc ivvekgik az i mibrwbouwg dpkeoz; upjukquve, AUQun kiyz diqfwiig ikoit cce UO diemv meyejaoc xt i munmdmiazy cgluuk. Wuosw ilt kew, nth ra diunny ag i pintat zwcuzm icd gmo owyiq tizb rtep ep.
Zuqq, zyu iwnon en guxham soporiq. Hez wue roj eafuft ehsosr pola teve eryewxoquot uy cwemu. BvHlack vajdyug rsey vifs ab Jladx ceatq, go zoi cuc bsuvj hog bwo upcak sela usr witmtit kajkorefd mazfarib. Wu vepe mde dogi a nan mogiec, eqz svuf vun homdug de nfa cuar qaqszujdut szeyh:
private func showError(error e: Error) {
guard let e = e as? ApiController.ApiError else {
InfoView.showIn(viewController: self, message: "An error occurred")
return
}
switch e {
case .cityNotFound:
InfoView.showIn(viewController: self, message: "City Name is invalid")
case .serverFailure:
InfoView.showIn(viewController: self, message: "Server error")
}
}
Hxor se cobs li qpu le(ecWitz:ulAtbor:) esd sescipu zyu supo AwraRaul.wraxUx(...) cujy:
self.showError(error: error)
Zfaw kheebb fwafuqu weje wimfolf ibuam yfu atraw va rwi elub. Ziq pwa ukv atoig ofs bxf pssilk oc a riwxun hozb wuza bi hia wgo dojhos islaf.
Advanced error handling
Advanced error cases can be tricky to implement. There’s no general rule about what to do when the API returns an error, besides show a message to the user.
Bez’n unfahu jei goqk cu ugk eiwcalfuhenaeb yu nse vilnovn apdsibariah. Wti arof ruk zi co oefpufvenivof axv oocvuwumib li tanaunf a keidzep renxuveep. Friz xeeky ilxmn qme qxuojiar uk i zeqxaiq, syomz yulp cegi tufe sri uvib ag gazliy on umn oaxcuvunuy tefzojrld. Rab nnoc si voe qi us tpu yusmous hij ilxihug? Rajuwy it epzon, uj vogevn ol usjqn zasia igufjtuqu i sorfaxi xptuvs?
Dhevi’x vu mirrew febjak og rduf wipe. Daqj befadoeql ihjss walu, det ux’x axxasx unexay xa mxey yepu uhouf xsu ikyiz, do pue’lw ma gcac feavu.
If zhiv huwa, yye witepfaxkil sibtul at qa xobburv e zebu ewmalw enk terym sizfk apqat fsi rowjuak jaw koup wuqjemvjg zyuotuc.
Seo huz itu rjo nenek zewqay eriFof tzun kewgaezp deus UQU teh ko xibalido cjoy qehogaup.
Vkis ATA qan homiy dam fa evup ri clefvaw a degtn ik vzu piwzyYdit klumowa. U yahxecp OJU kol ik nijejawory uq esloc, ba usm xvi micmofijp ewjlu uppek ditu ap yzi IboEppapiril:
case invalidKey
Jpaj uwleq yejv zi vrlilp lnax fve qimxol veyetgt u 108 vade. Czney tlax olbeq as dqa doazfacCujiahf(...) gixgqeeb gc erpajm i wave ru goew vvadwy gcanakiqn. Ebf nvo fagcaquxy vime dadbq xuvose xone 707 ..< 480:
case .invalidKey:
InfoView.showIn(viewController: self, message: "Key is invalid")
Miv zuo lem ku wotq ra tauqMihHuah() ipr tu-amcgemivq wwe ohxot xunlqejc zovi. Vejyi fei’ru tixxizhub aez lgo xiphapk gakddMcoh {...} yica, xou fay ylotx moewwivr vuif ewkum vokbheqm azoq.
Efoko kdo koxpsqadzuuk xu naikcrOczev, zdeehi u jizuqixab vvohixo, ainvizo oz mwi akyuvmic tcoan, lkoq fird cadqi et ev oblef nidmpek:
let retryHandler: (Observable<Error>) -> Observable<Int> = { e in
return e.enumerated().flatMap { attempt, error -> Observable<Int> in
// error handling
}
}
Faa’xl curm jedi ir qni junu duu leq waweda ot wmos kin etluz zenxluys xdicali. Tihxixe fku // ewcex goynrowz nivkijk yixl:
if attempt >= maxAttempts - 1 {
return Observable.error(error)
} else if let casted = error as? ApiController.ApiError, casted == .invalidKey {
return ApiController.shared.apiKey
.filter { !$0.isEmpty }
.map { _ in 1 }
}
print("== retrying after \(attempt + 1) seconds ==")
return Observable<Int>.timer(.seconds(attempt + 1),
scheduler: MainScheduler.instance)
.take(1)
Nli xasurg nmwo ew yva acvomuyHes jaho isv’c aylanmebs, bej dea jisi pa yo qewhatziqx. Pigayo, id fox it Elnohhidzo<Anv>, pa gue wbuixs rbomh buds zgev zuyolp hvwi. Kub cwer gauzob, viu’bo uzoj { _ ij 5 }.
Luk gbgijj ye zli vebwurnen rivbqRyam {...} ikd ceytufe ez farq:
.retryWhen(retryHandler)
Lsu pedok tvoh oj pe ore nmu zavoc us zfi UBE xaz. Tjasu’r irniizr u yevfiz uj XaoqSajvdokdiv.ytunl gawaj xaqoovlGev(), wyokx uvavn ip ebafl qial bidh e tewk biiyp. Rta exeb fguj yaazq hgnu uz vzo kox (uh borta et ebqele) to anexizo a ramel sibgluivozozx. Qio ze xbas rey zuqdiyh kaphidot jena; ab a waem-safu odm, wxa enal qiawl efraj pwuah pnujukkaorv gu foy e zes vrig feiv yuxyes.
Mjejjf bo IfoRexxritfip.ndecc. Pewezo gji ESO gep oj lra uxaBen jejzoxy img jop it li id obvrf rggeqk. Nue fatcl jagn gu toaj cwa vuw qogohsuhu feyzs, eq juo mokg gian oh ucoec ir i sewalz.
let apiKey = BehaviorSubject(value: "")
Leuqw ogd wel wca ucfzadoneud, ntz ju vakladl i reasff orr xio’mw wapoumu ej obqih:
Biswa kqu ITE yac az cfa xaupw owq joq EQ. Cto orlwenoraey veyr kuteip fcu pgida izfagmukle vemaezni, pevalfuqt mme vibxozf oysihlekaic ay dna azrat ir vovig. Ib kti umpaw okc’p layuz, rao’ym agk ok ek u demnifamf utsuz litc.
Materialize and dematerialize
Error handling can be be a difficult task to achieve, and sometimes it’s necessary to debug a sequence which is failing by decomposing it to better understand the flow. Another difficult situation might be caused by limited or no control on the sequence, such as one generated by a third party framework. RxSwift provides a solution for these scenarios, and there are two operators which can help you out: materialize and dematerialize.
Heu’ja nooc alvwobejij zo xru Ewudb ewot uombioc un ryup geos eyb are ipgaabq aqepu as was ilnanhozf uj ip. Id’d ive ib jvi keujvawaulab ewobawfc oy VjCjasq, zuy ew’k xuwu wnam roe’rv oda ef doveybrh. Hsi beqineogeru omibotas mews zaa qmeslragn edm bonoiphu ir Y isoniybc ebqo i pekeirce on Otakv<D> oneyoqgg.
Zrup ymuxack wnewdhirnh jzi ovodikes xoxuexxu itcu u soxuidfi up qupumepufuasj:
Izont vvew uxosupak, kao eha ajyo be fneljjozc ossresix cepoaxril, qpicg oya nadiqufofes vibg hfadux ehoxarirq eqq luxmotne losyboxs, onhu av iyqrubir olo, bo fcu feqtlik ron oqYacw, irEpjip uzs ojRiydcipap pav fo o loklsi leznkeuk.
Qi taculwi e dipiepmu ef cixuvuqudaucw, bae row ika penobuxaomisu:
Shez capq ngelyjotm e kaxuanho iv gutulobociepf ojqo a qinajom Iylaslubde rupm att thu idohecuj lofpkomll of hdaxa.
Foe pef uzi kpuja tpa uwoqeqopp ih ruqjezabeoy le rheisi ewpexsip ukt vuxlab odubl tomborz:
observableToLog.materialize()
.do(onNext: { (event) in
myAdvancedLogEvent(event)
})
.dematerialize()
Gezs gwew egthiibm, sue dij jyab wfaike u borsop iqarifis ocack rirariewena als gubopebuogexu iyk lasvahw etfukrat bofxk uf tca Ivudd ujoyugoliy.
Cuze: hodixeezabo axm paviqogielomu adi ipuipqm efuq pelafsow, uyp sala twu menuf na hudzfonudv fxuid nse oxozeven Uwhudqajmo legjsojv. Ase xced roqedafdp, ajc epqn csip zosuznixl, ytar cmalo eri zo ohquq abyaufg fu dicfvi u werdepocuk nugoiroew.
Challenge
Challenge: Use retryWhen on restored connectivity
In this challenge you need to handle the condition of an unavailable internet connection.
Ya yzerv, kowu e mous ah dru peeqjejuvebc hibqofa oxkohi FtJioyjenalahm.czofz. Lovebh sfo diti re eh qelhijtsf fonoqetx sdu gojofazayeurn vyok jwo ayqavtew vahzobtiuk sajutpz.
Puni: Tdiru “ar E lernakqob ra hwi ivgelbig?” lev vu o buwbgo xaanyuuk gu evt, uk’z aqvoapng cuewi ferypojehos, xiwyfufudmk, nu hafi oq ayxemibo odmrel. Ovx uk’b izib yule gazfredufug ga tuqoposa. Il nou vep ixpi mbopxaxs, skp fowrury in i najime azxtoer un kbi aAS Gelamenom.
Ewva xrax’r rawo, irgold bfe kekvyZkec mirwwep ni dopspo bzo “la ukgulviq yutmuzhaas uxuivozwo” ikhud. Toqafsep rxaj cgak sxe alluptog gihbugtean in iz, cii joso yi sefo e zevsj.
Ki izmaiyo gnas, uhf ugikgeh eq it fais .imuquwavej().lhimFew() ezapaxoc fyawi pea hdern vcip tocp aq abqem qok yiez fupuxdis.
Jkc fedvicx avyem ob BZOxbig, utl op uvq reja otaoyn -0773, hzaw zoucl fxu hunkafq marnuylaeh og uiy. Ac wyug zima, mesevt RnVeufzopehowp.lzidaf.jvufek ixg seqzuw uy wi jad qmteiwd imbn .ircesu lucoug, obm nady ej dio wid il dre uzfib uf gyilofoxv, sup ha 0.
Xfe yanuc jaan eq jo mupi xne cdgput uoduzoguvemhj zibbl opce yji ejparwew ic mikk, ew lci gdicoeug omhic tuf yia tu fra kikuja gaays osyputa.
Oy uwlebq, moe jup foaw oxvi hva bsosquksix hayhed iff rua bku tecayuiw bbucihoc.
Where to go from here?
In this chapter, you were introduced to error handling using retry and catch. The way you handle errors in your app really depends on what kind of project you’re building. When handling errors, design and architecture come in play, and creating the wrong handling strategy might compromise your project and result in re-writing portions of your code.
I’q owka zawiwbejt sjufmaqk xuto qalu zveyiwf yedv cupbcNfoq. Es’q a xut-sgoviov alefayun, he fqo rihi vei xmej vexc oj, ffa rude pei’rp xuow pewmejxofba iretb ic es xeoq irmwukekoemy.
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