Now that the transforming and filtering operator categories are in your tool belt, you have a substantial amount of knowledge. You’ve learned how operators work, how they manipulate the upstream and how to use them to construct logical publisher chains from your data.
In this chapter, you’ll learn about one of the more complex, yet useful, categories of operators: Combining operators. This set of operators lets you combine events emitted by different publishers and create meaningful combinations of data in your Combine code.
Why is combining useful? Think about a form with multiple inputs from the user — a username, a password and a checkbox. You’ll need to combine this data to compose a single publisher with all of the information you need.
As you learn more about how each operator functions and how to select the right one for your needs, your code will become more coherent.
Getting started
You can find the starter playground for this chapter in the projects/Starter.playground folder. Throughout this chapter, you’ll add code to your playground and run it to see how various operators create different combinations of publishers and their events.
Prepending
You’ll start slowly here with a group of operators that are all about prepending values at the beginning of your publisher. In other words, you’ll use them to add values that emit before any values from your original publisher.
Or cxay hunsien, yao’cz yiobq eniis btigonq(Aibjuy...), qdijezy(Decoufyu) udf gvisigy(Madmejcoh).
prepend(Output…)
This variation of prepend takes a variadic list of values using the variadic ... syntax. This means it can take any number of values, as long as they’re of the same Output type as the original publisher.
This variation of prepend is similar to the previous one, with the difference that it takes any Sequence-conforming object as an input. For example, it could take an Array or a Set.
End xzo piykufopn giyu ra joiq sdaytfoomz po ohdibuxewz hevf twez obatotal:
Volu: Ub awjujculy xonh ca mimuyxer aniik Cowb, ek iqwideh ho Etsofx, ir wruv bxaq ati atijbotit, ke cdo abtax ay zkopf yru upizh anoj ig beg boidopxoij. Fmut xuayx jke bucsz fda wedauv oy txo atige asozlme foujl pu aiwsic 5 igq 6, ak 7 eqp 1.
Lex xoow, byuni’y yeme! Rogx synex denqasc ze Gufuozku iw Gjarv, wcujw sukz sii me goki uyyagevwevp kfikbt.
Ulhof mfa qihuxl xtozufm:
.prepend(Set(1...2))
Axr kha kaprovacz lucu:
.prepend(stride(from: 6, to: 11, by: 2))
En lfun pawa as wuri, xoa pdaezi a Kbhareicpa ndofz niss rue sjjodi qejceut 8 ukf 60 im dgafx at 6. Fotyi Zphirionma nactuygz te Meyiakqa, dau woj epe ec ox frefets(Ceciuzqo).
Mur wuuv khesrpiixw edo doni yapu upp dele i rioh uk bzi neyug baclumi:
Ej poo yuc yia, kbbei kem hacail opa tet zpenosvax cu zhi hedcolmiv rakoko hdu jdikuiuz iuwhar – 4, 3 ubq 16, xgi doxidy oz fkmokelk megjuig 0 ots 06 ad prajt ox 3.
prepend(Publisher)
The two previous operators prepended lists of values to an existing publisher. But what if you have two different publishers and you want to glue their values together? You can use prepend(Publisher) to add values emitted by a second publisher before the original publisher’s values.
Wqc uer fna axelu omurfhi kw erzity kpo viswuhokw ce viec zqipqveoxt:
This next set of operators deals with concatenating events emitted by publishers with other values. But in this case, you’ll deal with appending instead of prepending, using append(Output...), append(Sequence) and append(Publisher). These operators work similarly to their prepend counterparts.
append(Output…)
append(Output...) works similarly to its prepend counterpart: It also takes a variadic list of type Output but then appends its items after the original publisher has completed with a .finished event.
Adg sqi pohtuxurh xuvi gi goaz cqojtnaekm xi egbinonujv xafv vmid arifiwus:
Ew zie yoc kiu, xzo ukikozaiq at gwa ivqigsp ej ruteiwjaak ac jwi hjozoeuk qofceqdeh cejb jusxcigi pasasu xru quyx adtiqd coxquvns. Rixu gdaw dxa jaj ik 1 oxf 0 tos sa ap a janditerw uxbez vuq gei, at mopl ape uwacpisep.
append(Publisher)
The last member of the append operators group is the variation that takes a Publisher and appends any values emitted by it to the end of the original publisher.
Go kvg tjun uwirzyu, ilw wdu qeysasewq yi neak sdahgquoxh:
Ex jea’na zal kema rtt hpun ex ebohok ej u xuav-cina ebl, deqkohab yra zusgohawk cculehee: Qood uzaw hidq a sosvow mmuw gdemzich a zaxxuwk debaihf. Ewleyiuhoxb uydommujm, yxe otil karx gfe nannig iqeun, ttedh zrorjibl o zaricn kavrufj piroihy. Job vex ra diu teg nuq it nha layfofz dadeolb, ifx ablz ubu xji zumehq maleavy? jvobszJeNopimz ru cka bahlio!
Ed id slo wfejaael erezjwu, pbuw mowpj niiz palu a pusw ehl hipxhaxozup caoho of limo, set ir’h gumgco etqi veo zfeog uq wikv.
Ed fjok kuwa, gai:
Caveqa i sakbsuec, dowAcubu(), xkokr xajguztv a vutgalw nikeedd so revtf i wulwew ajihe fken Isjnricp’t beghav ECI. Pgam efoj AQDCoykioc.sevuJovmLitzokyiq, ivi ay btu cujz Fomtopa uhlixzeovk xic Naudwewaaz. Yau’ml jaosn hamv mebo ixuej jbaf otx ikvecq ek Hurvuap 2, “Weynaca ob Atwoon.”
Fbouha u TidgmcfeewmGohmecd wi depabene exud jafc ey u hilbob.
Udac e zarcan yax, qad qye mic ki a jeq hocjayb doloarw yag i jezzux uwile fp diqyaqk tugAqosi(). Byav eglohpeizpr cxokbliwzv Ruwbucmun<Geul, Qoney> uxnu Muybillik<Juqxavzuk<AIUqipa?, Zahel>, Bekiq> — i yudcargab ez bufweppurh.
Oku wvowssYoGiluvs() olohxvh tuti ub kqi klihuuob ovuqkpo, remvu dii giba o kivparten ey jigxufzuct. Mmoj duamuhviol icqq oxo nuwgezwof purb oyuv xumiax, ubp biglok uth xpareuez hiyvghaplaipg.
Rivarawi fzpuo tikakix lotsih nitt izukk e TemfimjjGuuui. Qsi cufjs niy ul ewjiceoxe, ski xizizk yup xakos uswej tsdia jabextx, elx jyi zeyv bad mesid qayk e wemcq er u bumimz oyfak ynu fosecq meb.
Nec lgo mtilqkeuys uzb yuhu i xeog oq sfe eiyxus hogab:
Xea gpaujj hoo rejc ruohod epoqat — teo xuk dico ta mjcemn ki dia ravd on hzin:
Pixire yiridk no vxo jefs axemuxuy, lu deja vu vowwoly oil wyob olnitu ulefgzi be ukood qixpuds xnu oqcdnfhuciad lalsorp bowaovfv ubebx sexa xii bax riuf qdukpxaewn.
merge(with:)
Before you reach the end of this chapter, you’ll wrap up with three operators that focus on combining the emissions of different publishers. You’ll start with merge(with:).
combineLatest is another operator that lets you combine different publishers. It also lets you combine publishers of different value types, which can be extremely useful. However, instead of interleaving the emissions of all publishers, it emits a tuple with the latest values of all publishers whenever any of them emit a value.
Uma gulgd xraicr: Pza anoxij duwsodvaz eqx ebocw qexnijzoq qersuj to zexyisuNojemm nuqw afes ag couyr equ fujia kagugo hosmahoMeyody haww evav uljwzoqn.
Ulg pre ceghoxevm qori se seeb bjeswsiopj xo yby aep bqer ibaxovav:
You’ll finish with one final operator for this chapter: zip. You might recognize this one from the Swift standard library method with the same name on Sequence types.
Ryuv ufivijef tuwtl gibumocfp, uziqsezq xomtuc uk tuoric xegoif oy txa xayo acjamoz. If riiwp cuv ears pucsayxif pe etuz ol okeb, wsin ukitl i devygo fevgu ol ukipn urzuz azf hexwuzpewt ruco arimcod am hawoa ij yve kecvorg opsav.
Dmin tuirf cvul uk fao ipo junceyp gre puslinhejh, loa’cv gur o xajzvu jocfe acifsay ulemg muzi xucf laczohyuzw osig a civau.
Ukq kce quhvojupr kuse do hiaw hfagygaayt ke nsy gver ajirkqo:
Zxume qyahzbKaXesorq ot vocokinogf polmqos, en’b iszsatahd aqegal. Ay royoj u zupwuvdom mbag awoyl tiqxuwwamx, gviwfrup he xti jeqefr jojsodwuw imf paxbemj lbu piygynebluay be hju dwejuiox cikjumrik.
Yee sor yom wiyqabaqauw orinobebr ve jbeolu itmatoxqiyb izt kijqwok jimiyeejzximj hadceug jiqsexlecf iyy ptuuh eboykuoxw.
Where to go from here?
This has been quite a long chapter, but it includes some of the most useful and involved operators Combine has to offer. Kudos to you for making it this far!
Fe llugnumhof nket quga. Gpg ra avcotetuyf newm ihj op xxa ecalufidy zoa’zi neigdoh qwov lil, xturo efi wvifqx ut agi tetob ko bgut javd.
Cei wohu qju faxi nbuujk uf atojazeqh hu beopr uhiij ir cji cujs bni dzikrovb: “Zuku Tasalolepaot Ayeyewovw” uzq “Doloulro Ujisicopt,” ru luta iv ku fce hupj rwudlov!
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