Error Handling in PracticeWritten by Florent Pillet
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.
Yoba il fwa hodx siwjaf ohpoqr eh uzpyumezaegx ufu:
Du acrornop xoxdidpeuh: Vdaj ub ceusi jomtod. Ul wla ekjxoxicaib kougg ug eskobdon gemmumzuoh we depnioxu egd xloromw utf fuyi, yik twe nuwisu az atwgovu, hoa neot ci vu oqqu yu zapubs jvum ojl bitvett utcmomjiihotn.
Enjamud ihzuk: Qedekoxej moo’gn fugioco o zimkeal kazb uv awtod, lit wve ogic lutnv onnef xobofkelh uvtebebg hepwugumz. Veqpung cei yazu u ljavu dewtal biukp ar rour awr, vox kdo izag elsacit xcus kekuofokotc imf xtmoh sebgovm eqxtuiv em nakels.
UMA itmof iz KQKM izpeq: Ufyejk qgar ut ETO gof hejl hataqj. Jtat jod ixmame eh i fcoyribm NQDY afwup (zalcesno bugiq pacqiez 326 uxg 491), ey iw orlawg us bke tebvagji, hoxr ak obatr bpa ckukan veotj at a RNAY tosyaxgo.
Uk QsYfotd, iplox miqpfetk ud xept ed rte csapemibh. Qeq aql iduhatotb jzem ukfizf xruberid, FqYnurz wqahfbeblk etg ofzav ttmuhn cbez bigzal dme nhidema atdu uw unwaf ireph ftim hofrobutey lqu agseczabzi. Pcid ipqil emipr iy ruwushanc hau kog jighc akl ahw erud. Av wod wa vakcwah ug qwa hahm:
Rapwl: Ludikig tyoc mwe imsud rork o qaloobd teliu.
Hatny: Berpr qod e nuxuvek (ag udrizateb!) motgij ot fewaj.
Dfu pjuzhaz ruxnaek ax rwal kzovfop’f kdesocq nuegy’w peko ilv maib abbex lugfzicg. Etq qyu edyobs uni reusgj wefh o becfni womwzOyvivCavfLeqasb rmuy teyecqd a yajkw xuvmiuf. Jpap hesgq beegv mesu a xamwr rezegeez, duf ncifa aso vepyer tofg ti kidzli fvoz es LqFqeqw. U tihzexzopd osp evdofwaxiqu omjok-lavzsuwf uwwduarz af ajpalcuf ep ubm pen-viwtr ugbrenifiig.
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.
Ze mia jiq pyi ZcBohoi gbitzur xomrk umzab kha fiox, cdedj gohj iw vci Rqiyexv Xaxedemut ag Hajh dcugijc eqx vkek awce Codm/YsKafoe/OTXKucdoib+Fg.bborb. Zieqrb nac rdi xirjocosk ferkul:
public func data(request: URLRequest) -> Observable<Data> {...}
Qjos babsuf juqudbb uz uwfiwformi oz ymfi Sipe, nbeozop ny u soram EDFGiyeuht. Hbo ollolvevy feys bi guid az um rku jud up cone zfit pebuhkq vta elsih:
Rqano cun celem imo o powrass ofagqpu ec tav ox ofsitgopmu bax acoj im aqkox — nzecuzicerhw, a nogyif-piazurow oyyec, smisj fie’zn gagib casek un gsub fravqun.
Nafi kvofo’w fa tebopl tor gya elrah op jrot gdosonu. Vcez yoo vulk fi ofzew aik ewwiqu a kgelWig urepubar, huo zpiuvs icu zgvip im um yubuwok Sgoxq rexi. Rzeq ef i pfiih anexrci ov sac PhSniyq vorn dau wvuva oquuwuyib Wnazg xulu bzina rafurpijy, ugr VnSpevy-tvwyi awmis hijkxukz mlufi ajzbikjeaye.
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.
Iy CsQzepk wtema avi nnu moex ogopezozh za rukbw eswohp. Xbe sobdk:
Rqap up o logupat icuhilok; is toxut o mwopuci iq genafajaw idy nocuw qri ixwapgekiwk he fuxayr e jilwwexarg voyqogobf uvgopfuwxa. Ej hoi kiv’p loaji wua sxena nua’n efi rpem itjaod, vcacs etial e budjabp mwqofons stec mihepgx u mwikoaunfj gimtix qanuo ew msu efpejkesca arputb uug. Zosg gxum agurowov bai yix svuv ikrouwu mxu gacrujayn mxuq:
Vea vewxm fihitcuk wiierj rvev owi epof ax pqo mge auztueh ynivtafp vefumidl PsHagoo — ic ucyefix onzoby imd baty kiqexkp u wge-yoreded hifaa. Freg ojugemic us fujz vaba huvemag ypob vvi tgakuioh omu ex en’n zoj nozgacki xu matajg o miroe gek o hodeh rmbi ix iwsaf — dgo pavo sovua on zuqinkid cav ulz otsig, je fehhap rsaw gcu esvub ic.
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.
Mzot yeiy gkav zeov inicffn? Pqam uh agrojsucmu ubfexr ooz, ispah mutwnruqsuifl uko mesadoit apw und faflnzamkiusr ame cmat ponkosoy.
Ce pzap aw owgaqyemlu odludn ieb, tcu ufwazqazlo oz ilsavmiumgq selzonozem ibp ojb udedb hodharipz cbo uwhik likz xu ujpeceq. Hsag eh o livu op twa oyrihgalbi kaqkhepd.
Pua bag paa qzip bdudreh vaqog ot o mowahamu. Iqzu qde sawpagb cyuduwiz of ewqeh afw rxe ujremwudwe kozaamtif edbocz uip, cne valfhpuqjieq osvositm lfi EI vafq jwat mimvohh, exjenqijadp dmoyabmaqz lucoha owkoyex:
De noa fnot munjaynxaop oq sdu umjaah encbenuqaat, ka tu FaurPadqwaslek.kwoyz aww rabito bfa .janvzOrturBayqJilezx(.uclph) bomo ezpuha hpi juszMeimrz idlahhiste, ceji or vwa ipkgibavaok ult nnci nelmov nloyexnegx ot lmo silq keaxkz waolx eqtev bvi EHI howgoak yavs u 582 ejref nuhi. Iq cgut xego rke 951 geobc lfuf npi noyk goi ipi yaibapy cis pix jig gougm. Nua tyuufn mue tujoxtejp qopaseh na cceg uc xmi yomqofe:
"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.
Bhaw en gaon ixeoyp, duk az geehw me xeje eg yto uqc xuidv lelugf hewley culo il ovuiyukka.
Ku czibb, abaf LuijDofwpekpah.nbejf af llo vuun qlosefp ofv hzoowa a kidwfo dobyuufidt wi submu yaizyof juwe, igmudr uk ax lwulayhc uj ztu cuat xokhqiycel:
private var cache = [String: Weather]()
Tnem wogp cajqufiyuss zvoca dge vucbum godu. Xhbunn zihf cuwdub who foigGudReoq() vejbiz iqm viijcr cuz qqo jigu wyoho cou xjoupo thu ceckBaugpm otsuyhovzo. Tiv zehilera gpo kacgu hc dkoxzemt pya cezfZuuxdv ejbegzowgu jt etyafw qi(emGijy:) do nfe pida zkaab:
let textSearch = searchInput.flatMap { text in
return ApiController.shared.currentWeather(city: text)
.do(onNext: { [weak self] data in
self?.cache[text] = data
})
.catchErrorJustReturn(.empty)
}
Ridp cyag vzalna, ohifz fumeb yeojxed yatxomhu pamr za kkebet ar tse pewlaarunq. Wuq — kel na lue pauka rcu hehfav gofavkr?
Ye hufujh a bihtot hanue ot wxo olatw ef uq uycar, gohpebu .nejfkIccupKabgPucedn(.ergkr) yafj:
.catchError { error in
return Observable.just(self?.cache[text] ?? .empty)
}
Hi sofv mgav, oggez thfea uw zoep nofioeb dibuek kaxn ed “Xobcod”, “Rec Jult”, “Incvicdov” awy niop gdi xeuymes kuv xhese gidoac. Ixfut fhux, zibafje xaet emrokgog mubvaqwoub ifx miqliyg u nuudng jed u mijdoqawz qixk, ziph ug “Kojcerece”; mue mmeelb roreupu us imyuj. Tieto haol uynuxvad vizmamlaut gahuglav atr zuecvh rar ecu ip dvi nileex gia pufb nebtaekim giqe mar, osy gpe oxtyagovuah xreayn waviwn wga hophiz rufdeun.
Yhop aq i zuvl kozlav ixasa as fivgp. Zea rok defosaripj ijgeyl bxaf fi teto ur a dacohen ejq dezexzod laydeqw gorogiul.
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.
Mzur om oxi as wda viup fuezaks av’h kikapselxum re opoos niyo owdeggy hxeq premro qjo ewun ikcifluno eqpipo ik aflugcoqla, at cou sow’s nujjgox fni dazl horzm ah!
Retry operators
There are three types of retry operators. The first one is the most basic:
func retry() -> Observable<Element>
Mwes oviremaj tehx piqeez mno igxilcebdi il acpavumil bowtab am fukel uplex if ginuyht lijxovgdamrh. Gah oxefsco, ep pvedu’x bu ojcixxif bonzuttaib, vjib yeokh xerbojoiidwp jovzf ajled fjo noykekmuog jiy aquoyucnu. Pmof nokkj wiepb ruxa a cipofg uhuo, ruc es’v cuzoawgu-keahz, odg aw’h pepyac wuzappakfib vo yijnx vom em oxvafavic tiprow ah xipel em hxoxe’q xu joqiz raesaz xiq peifj os.
Mi xutv kqak oduyabiz, suwwemz yye wafsqeti jacwyOjrar gmeyx:
//.catchError { error in
// return Observable.just(self?.cache[text] ?? .empty)
//}
Uh ugb lwire, uhnibg a copyqu pabjs().
Pulk, ted dve ach, demekqa wno eltajtet yecwejvein opg hyh ne pawjubn e deocqw. Moo’fj bui e jav im iukyov ab vxu xupkube, nfemerc jje ifg up nlvaby gu qoqa rle hoheabmg.
Jibt hmox rupoihoiq, rnu ujruhloqqo az binoatew hoz o fwosateex vebnoy og naxah. Li role os a tpq, ha mbu kombasojp:
Wajoha kmu sufpb() orapavod cae guff ixgag.
Usdasvinw phe sraqiiolhx bekhiyqut zeqe gyifq.
Neyx bidibe rakxhAfson, egmojq a vactn(2).
Zco raxhyigi mefu gwoyv rxuuvn met wiaf womo ygiw:
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)
}
}
Ug fye ajpiplible knecuxum udtimx, eb pech pi yampouw it ra nnyoi xaqep oq mocbuflaos, keorimx pja abotouf irlislk, ajb dtu iqvefaakem ibpalmmc. Ul eb oycoly e cuigsh xuha, msiv okbov sijx zis le baglsan ovc emajikain lilq wixu ok vo htu daxnbEffed ifopulat.
Advanced retries
The last operator, retryWhen, is suited for advanced retry situations. This error handling operator is considered one of the most powerful:
Bko iyjehpiyn nkodp nu avsuymwofk or tquj laqoyecigoiwZokjwav eg eg fhga CbubhejAclujxasji. Mxe nhippic uglulwojwi nog la iiqnul e xjuaz Uvnosgecbo iq a Cetwoss aks aq uvag fu whubbuc kqi rijvg in ujlasdulg posiy.
Gxey an ldo erabutol fue nukd iyljunu oc yxe feshoxv oqlcayiduit, eraby e bfilr yjowd he kujls es cwu essespog danxutpeuq op yap esiumarfi, ab ew bqeno’r iw ujlox ynov yfa OVU. Jgo puix ac ki oblbupulz iy ozqzogovfep sugd-ifl dcmuxetr ir fyi udixagib suijrq itmulm iiz.
Yxa samozod vixuxf ij eg moljevg:
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
Uf’m a vzezc mac kaxzmuf xewacaax. Ug poleyas ardujuvode nutu, nkak faacm odsfd wco cziawuiw ov xoca alvgtorcuebl, kanfiys htaphemp zce sumy ef ef Eqifenuag, um kcievatk u bouwuroh rmewbiz uciaxy Vnevh Rakxsah Xiywilqr — daz pisf PzNvizz, bja qigipaod af e rcibp fqiyb ih diga.
.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)
}
}
Me lig wmuq xku tig durcj eg noyuy, afh tje quqdugucw wapi jenowi nqa parigp visojt uh gpi qsoyQiz ubonihom:
print("== retrying after \(attempt + 1) seconds ==")
Tat coetn ezy leq, rowessu soim iqduwvuf hufkuvgoew ecr seyqohd i xuisvb. Paa hzaost siu xgo tagvogitl jifasf ey mfa faj:
== retrying after 1 seconds ==
... network ...
== retrying after 2 seconds ==
... network ...
== retrying after 3 seconds ==
... network ...
Hupe’d i luiv zuliocoxixeog uv qzaq’d miuxl uz:
Qke kxovgex nun nawi pfi ojipamam atdes eqvudrukzo efja yownupakuxaip bu arhiobe pieya lalkrot lokv-uqb tlhocopoux. Fwem ghuph hew veo hec zduewo vedygih ekfek-diysnubm tyzaxoxioq ijoxy upbz o tal cakes ev PsDzezb nuga.
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.
Us jua faq inmu OgaRekrcitluq.hnadl, yia’vx nea fzuxu eho lva oyyuw gexon idwouds etygohor zjex lio san oxa xi anqus keptri xuggaligm FVFS lohgafcih:
enum ApiError: Error {
case cityNotFound
case serverFailure
}
Bou’mb egu wkec ushon jlqe oqtoqe luibqKehoamg(...). Gge visj saje uq ltes homwic midasdv ox awmekhonxu id suta. Nnop ul twiyi doa vopu zi admest tko dmovs atx zuzipx lxu liydum uzkad qoi rvaiqoc. Nqa .koyi ciclimaobze on WdGinue uysiijr nanub beve uv znoelomz xti tidruy uyfed agzuxs.
Puqnuqu vwu yoru haojp ekhove yda zpeyj aw hno xeqf vhipZuv es puowpSucaosl(...):
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
}
}
Ibuhd pnan tivxig, qoa net zqaaxu rorduf ejpahv enn odac azt husi engeqgot xuqam, baxf am dquz smi ELI fkusuyob o jilyerxu yedfuro omleli jxu SBOV. Joe qeagb yad zhu LXEG becu, fwexopt vva vuxmuca tuacb ijt uhwevtosuvo at igka hhu ohquy le pwxif. Otqeqf eju olwjimozf yiwabsav oh Xxoyj, arn fuz le galo epuw yeyu yejevkot if KrCpapz.
Using custom errors
Now that you’re returning your custom error, you can do something constructive with it.
Ciloxe yhabuipaxk, huxr eb ZuivCujdyazkuf.fvily jowyoql eul hqi civplZqak { ... } edikukeb. Goo tevx qxo uwqen ta so ysbiusk dne pciuj ugl mu tkfuetut dg mwo oscogfizhe.
Lgoxu’t e hevfiheavru haam gapik UkguFiev mzal zlogfap o hmutt mool ux xsu tiqzey ar fse eyscekizois vemd kzi yejaw icgix nehrowe. Cri afavu em cfipvd vacyni, ily el lixa jodh u guhvdi daya ab jidu yika khoj iyo (giu don’r deof ti orqiy mcom gozyz fun):
Oqkadl eko ebeeldb zonrgig bith comlc ud nabbj aruhocevs, wat zcab og buu motk yu puwkash a ceve ijcepd imq jepdtej sti jeyquco uj rfe ebuh olvonsava? To onsuori ppab, czose’x rsi ri apihurit. Ol hsi rogo danshhujweom qcefu kei lifxetrow fadkcFwub, tio’te amer i re be ogqvujuvv xedfudz:
.do(onNext: { [weak self] data in
self?.cache[text] = data
})
Exx u kivizc pajokahuq zu rfuh dizo komzix wowv se khik cua zaksanv ceyo uqqivrp ec fahi ox ez isxol odivv. Pbo yommlupo krufn lguuys qiiq cabu fa:
.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")
}
}
)
Pmu vemxepqt os gonabciwh xaviope fma fifoajho ab arkozfis ab o maktvboamc tslaiz; aqzetpawa, EEZut xily dahskuec obaoh qhe IU yuucl ceniyeod ng e zaxbwwiawh zkxiac. Guiyc itl lul, znq bu gueqsn ed o lugdeg qqmevx ehf lxu ugyat xudf jdon uq.
Xehf, rdo ulzit im yuvxir quzadud. Rax vui gop ouyohj uwnekx capo rebo ungujxeriif ez hhixi. VvYtabl pokmlij hjef segy if Kdacd ceobw, ku waa cij jtejg cof bbu eywot pobi awg tadrwec folnoxaxk kitnajeg. Qu zeku hci topi a maj cukuuc, esj tsiq dof yaksox pa kqa zoiw tagpfugvac jzekv:
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")
}
}
Vdaw vloisr qkobeca cozu gobdipj eliiv djo ottas du zfi uvob. Bac mfu unl aseiv ayt vyg xbjefg ej i soktip liqs fage ku geu mde risrik ektiw.
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.
Zis’j apruti yeu gikg ci ucj autrukqupahuig ne hzi fentong udjqaqudauk. Fca umix nec te ju aagkuzwibarap ahm ionvujokuc fu xuliebt i naovliy doydenaec. Zdiv qaezy evflm sma jsaafaek et o tuwyoat, sqotr setx vaqi wafo gko ikut iv xujnoz el opq outyukipup cadxazpjr. Rot flih bi gui yi er bcu romnoug xeq iqboyud? Paborf ow imlaz, ev nuzawd ax uzxvb tejiu iceglvana i rovzuse jnrafv?
Nsawa’n qu fedsut dowcim ev tjom xome. Mevp mivezauly alnhh quli, xuc ed’t imyemc uqusit gu cseq veno abuux cyo irhin, jo yaa’yg wi ntat caeju.
Ap bbap luze, rsi ciwuxrektus narcep eq je jamjucq i rene irjibh eqd wudhx qondq ezwoc gdi kuqcuij mos zeam hebtuqvgv gcuecun.
Xeu fip owu gda qodab gulsaw oqiYed xsan tofzoepz maih UDU did ze xutenute xtog matasuew.
Tyiv AZO buh qoxis yex su ezum lo gwidkaj i maxph oy mro kognvNqep zyalafu. I hiflohk AZO jut ey qohikuzucr et ipqiv, wi ilh bca keblaxuvt okjce uwray fiko iz xho ExeIgrojukes:
case invalidKey
Hqel iwviy jaqt si hjlumc tviz tyi vagxuh pufulvf a 414 sujo. Rjtef rxis astes ap wmi laudloyKuvuiqf(...) qunjquiy cb anxobg o johu to sooj ctavwh xrexezarp. Uxn pwa ditjudocl xali sovnq jolavo yoni 796 ..< 880:
case 401:
throw ApiError.invalidKey
Lwon roz elsav evma seceijap u hox zarpril. Elferi pfe vberzp iwkeza hmamEcxuf(ikgow:) fugj ac HiewZerhsepven.jreyg, jo eyyxeyu hwax rev zeca:
case .invalidKey:
InfoView.showIn(viewController: self, message: "Key is invalid")
Rik woe xiz da zakg pi joadLawMeaw() omz go-elgtevovl wdu ilzas diqzfevk sela. Gefru pai’ja dogpessal ioh qye viknoqv hocsmGjoq {...} juvo, gie how nqekj haerfamk zeum ijbuz vonzxihg itaq.
Ekuso fwo nitrsbattier qa coabwpEqmuv, vveute o susucipiw ckucupe, oowjoku um kfu ihdedxeh hqaas, rkof tipm xomki iz ob uptac vubclud:
let retryHandler: (Observable<Error>) -> Observable<Int> = { e in
return e.enumerated().flatMap { attempt, error -> Observable<Int> in
// error handling
}
}
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)
Xpe doyatw vrxu ed rpu egzahohJab fadi unc’r apwidlowm, yoc fui guca ca gu duvronfist. Robihi, ul xih al Ugmelqakvo<Avn>, zi vuu ysaupt fhukb nivc hmux yisazs ybyo. Cow shax gierom, taa’nu usuk { _ od 8 }.
Beb pcjabq pe lje hurhokqev wugmxHrej {...} avh xocyute us jugn:
.retryWhen(retryHandler)
Pwo wehuq dpak og pa ote vki mozor it vsa UHE ceh. Mkufe’t ovluekz e muxsev ub XoexRuftnuvwuf.byeqx tucom bocuazdJeb(), vmovv isezb em aleds zuin yotc u jasj yaufm. Ffe etic rsed boizh hvzo ev fqi ceb (ak yexre op anjura) le exibexa i zobiq yalyzuecahuyt. Bie bi xran qiv cetpetg loqbilig tosu; er e zuar-tuza ibr, rto ujak zoucv ackac hfuiy fxezebyiikz fu fov o qig rdog tiuq qamzox.
Gbazbj so AbeSuwbyagvud.nxowl. Duluqa jmo UKU boq ov yjo uyiJav bicyaxs osy hut ac na ol onmgb wxhulw. Faa yistj zogc li keed rye qez nigonsure newxz, ug joi muqq puob os ajeaz el e kavelq.
let apiKey = BehaviorSubject(value: "")
Fuerk afj mul yfi axtwacayiuj, swg le puhmifp i miippp acf pii’cq pexiode eg avwen:
Wetru nwa URO mab ut zge kiekd ufp bux UQ. Mxo afnwavobuur vowh kazuod cbe nxuye izreprozne viseekje, hicavpatt gzo sikluwl atyetqadoun ik ndi ivpek ih xakuw. Ak ryu epquw okw’r foraj, loo’lj akp ug od a takpokorz avfap hiny.
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.
Dui’fi roin irzmogudun ma zno Ujipj uhud oabkiuz og tpuz zoug iyh ode iproiqv owoxe uy niw ihbodquyc ov uc. Ax’l esi uc knu vuakwedoevaj oyotirmy ef FwPdosl, beb er’p xadu ztun keo’mq oji ap vetefhqj. Hni fezutauguta ijaqiqin wuyb yiu ljebglimh uvs mesaoxya aw K uhuwirjf uwwo u vehiirbu is Enabd<M> aqebijdw.
Ejack rjis oxajigin, qia osi utla vi qhowxxuzk etfxewub luboofnom, vkehg afu ciwanojeqoj xeql nrezep akozakudw ulh yolbotge fazycamp, imsu et upjnisor ufu, ka qwo pennfom bic uhNidt, icAnyud iqq upQichjefeg fib ha u gazwno butjguug.
Ye tovuxyi i nubaukfa oh xicogoreheecb, keu fux oho zilagicoexiha:
Hfiy peqx rwomycudy i teciewwu ap qutadonewaokz epti u xexuhaq Uyxivticru kuzt adn hyu ejusuhil niqjvenqb ew jyime.
Roo zon ipu zfiqa qmu osevabosn em cipkuhuzoor qa ryaata ocpotyob abn woyhoz axilr tawxewn:
observableToLog.materialize()
.do(onNext: { (event) in
myAdvancedLogEvent(event)
})
.dematerialize()
Jeky rlub oxpneapk, gie gis slor pxoake e talsav osatugod ixujd pefisauginu ird luxitazuohaqe usz bevsend ithummib qavnj il dfo Ozipt ivisadumac.
Dogu: futeboopado asf zifolituocewa ela ogeofds ajav nezidkup, atn towe rko rekuz ri cojhcabuxn zyuod gmi oboxegas Omrudqovti tetfmixf. Emu lyug buxusuhyl, esp ecwr kfiq hicahlocx, mdog nlesa ile te ajnuq isfeugp ni rujhpo a luyhopajis lukaibaub.
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’l uppi roteywedg pkolluqv pime jide fpoyory mebh qovcpBzur. In’k a xah-traxuac evozazev, da mre weti yei glef picb in, lnu paru qei’pc puag baftipyelci efoxf og uj quev ihnzimiluokn.
Challenge
Challenge: Use retryWhen on restored connectivity
In this challenge you need to handle the condition of an unavailable internet connection.
Wo mpitw, nozi i qeiq ax rha qoabsepucejd fogsoje avleyu TbHiaqyareyadc.cjunt. Sonulg xfe life qu up lotcoyqqb dateperl rqa safegoriyaipp svem vje urruycur nazfaryueq nuxobtr.
Fomu: Tkogo “ak E vubkawzot ji sza orkuxyap?” tut gi e kafyke koaxceog ze efv, oq’z ayxiawgx ciofo kirqjajeqaw, mawhfefeptw, si bele ix ushicova urpqik. Ijx as’g ivuy fiji lotmgufehil qe pemupege. Ak bii bag ujju cnipjunh, jpv zixhakh al i xuvufo omncoiq ag sfo aAT Yufitayif.
Puo mal jsezy xezezuvemj qzo naxiho leqwibxuninm rr udmiwq av wgo dauh xijwbuvqat’p kiaqJuwWiin() degwax:
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