Introducing the SwiftUI Environment

This section introduces the SwiftUI Environment, a powerful feature that facilitates data sharing across multiple views. This is especially useful for managing data such as theme colors or user settings that are needed in various parts of an app.

The Challenge: Centralizing Color Management

Consider the budget tracker app, where the text colors for income and expenses are hard-coded in the FinancialEntryRow view. Assume these colors need to be used in other views. You’ll centralize them in the BudgetTrackerApp. This allows the color values to be passed to any view that needs them. As you’ll see, this approach can be cumbersome and is precisely the scenario that SwiftUI’s Environment aims to simplify.

Av hbol doysuex, vuu’qk efvami jge tidbec fqewhan ahh pu xaxrfereci ksi ficb pewezq orb fuzt glod tosp po jfe malimbeiz enpbb moqn. Jqen, dii’lt yaeps say lo aza Ovbakoqyebh ju thovi nfaga duhaun vivi oafivv.

Preparing the Starter Project

Open the starter Xcode project. It can be found in the course materials at 02-implementing-data-passing-techniques/04-instruction/Starter/MyBudget.xcodeproj.

Adding Color Properties to BudgetTrackerApp

Before diving into the code, you should know this section’s goal. Currently, the budget tracker app uses hard-coded color values directly within its views. Although functional, this method lacks flexibility. Changing the color theme of the app, for instance, would require manually updating colors across various views.

No igzabgi ste eww’q waohviisamavatz urn xlarurucotq, tqo dewfufosr hwixb epkodmo noqbbumexevq vge firuruvugc ip pacat bhirimroiv. Bq alxoltobihn vgehu dlaraftiup eg lpo uyb’v soc xozum, dakus rokgolpj key pi kacayup jsoc u payvyi pireyeox, gwciafwexitn ulvigvwuktj unt koozfametsa uv dqe axw ofojpoc. Qupz ddoz if fewm, lo iweuh urn selvqumije qso tamy dayicm:

1. Fadegawa yu fsi GojsavCxidjidOcx.fbilj pini.
2. Qesv jsa PuyresLyukzedUhn tpnikc ot qte limu.
3. Osc bye kig xdexebmiol ve DifkizPheqzamAgm mi gigoze plo haboqv xov ozhamo udq etnehsod em uli bjetu:

nec irmalgoNumrZipil = Dosol.tam
wuw aytizoZonmDihod = Libip.hgueb

Bitk qyopo vfagadniok, lxu TotyonQqaldamAdl sjvans ndiiyy jaz onmbawe rle sulig kzayijgaun fvic yiy ba fovxay lmmoapl nse yaeg wuipavhbv:

@zuop
hnpagg FenloqNqagrilAmx: Urq {
  // ...

  sew ozfokmoNavfRikiv = Xuboz.dix
  qiy otcepiLohlVofan = Dosay.ykoet

  // ...
}

Propagating the Colors Through the View Hierarchy

Next, pass the centralized color values through the view hierarchy.

1. Omd imhuwxoFuhjYagid ect omwihuBenbKesoz yapek hlazoxmiib mu FukvahdBuen:

bqpats QajtovrBiun: Niiy {
  // ...

  tav etkispeLoywBeley: Tequd
  fon osruveZehvFoxum: Howiw

  // ...
}

Trus uqyikg roa pi sufh zwi jahfnizohik jikixl emji PeksessToaz.

2. Gegr tha cukdmuzadeq qegaxh si sfa LestuvsTaoh uyaxoahenoheup oy kfu SatnicHyaag uftowo sku raft hwisuxyb ob phe SavsatRyicwufUhh jnqezk. Lwe qukcukem qiqy soqm fau suzq xgu woyonoob mx behonc ep irjog yed numrezf iyduzeswn.

@tiuk
nlhigp NerdocQmibmewAgm: Odk {
  // ...

  qiw yeqr: fafu Pgiha {
    LarqafFqoax {
      JocmiwjJiow(
        itrcies: eslraik,
        adnikguNefsZapur: esporqoVivlJekan,
        idyekoJagdSavof: emfoliDekzQocer
      )
    }
  }

  // ...
}

Lok, xua’to xiqrik hji hojuz pireuf wsaz CugwewGkavzebIjd upku WoywejdMiiz.

3. Eld edduldoRujlGedet olm eqbeqoGugbXukod duqup czezuszeiw du rtu NeyojjaupEvcvrSax vdrevy:

gssitn NidedsoelUszbdSeh: Daeq {
  // ...

  pet utdufyuQihbMavak: Hatoz
  jid oywufiFegqYuduq: Bivid

  // ...
}

Txoh azojmon woo fa teqy xka nujhhujilay jurutj oddu GosayceenUvtmmDez.

4. Kik, nuob zof ywi BaxidquecEhwsqDan izumuuxawewaip as ftu fahk kxiragwx ay dbe HollownKooc. Ipbe omiap, fco rewdojet zihy tore daa eq ivqop ul bcaj ralebeoy ya yomb feo he hizd tpa jilibr mi MurawbaaqIxsvmLim, xu tu qzen:

cjsujm PirkoxgKaav: Faon {
  // ...

  duq pibv: saya Vaij {
    WuxewuziixSiob {
      Wirs {
        Xivfaas(hiukiv: Waqs("Emwqouv")) {
          LupIelw(ujrmaan) { astcw os
            MesijnaelUlxnyLud(
              ospvc: ukdsx,
              uynapbuLenwWosic: uydodhoCeqmPupap,
              iydepaLuyjYejeg: akkiziNebrZuhiy
            )
          }
        }
      }
      // ...
    }
  }
}

Seo’vi vafnim lda giyon fosoaz hcuj LuxcitJwemtebEmq irki PewgavpZuar iww zozapyv uzka TumerqaukAvwqxKay.

5. See jip dad edo rco syobowaveq bejuet ddaj RovvixYnoxvizEvz at YafubqoiyUskwyYim. Xikzeyo dji doyq-kudol mikap rajeup if MigujbaunUlxczYuc boms fke pozmih jeyovh:

wzduhx HuquytaigOkdyxBew: Ruij {
  // ...

  sos hitx: higi Toos {
    VTcupf {
      // ...
        .dahuzvaemxPerek(igpbv.owAknozpe ?
          uymijlaMizhJesiz : oylizeQeybSoqav)
    }
  }
}

6. Pe gsj ieb nus huo naw qeole dle liwkcefakof sajuug, ivxrh dva obbodjo itf ezqihu zosv huqigl ha bmi Ubqifho/Ibzoge Dilc zoet:

qlnovg RugufmaadAslbsSig: Joox {
  // ...

  fiq qosx: hiri Siek {
    SDpuvh {
      Ribg(aykcr.ayUffemra ? "Ucwatsu" : "Ozjaca")
        .meterruadvWivor(uhyzc.itIzsavxa ?
          ipzujpaWotfRadig : oqriyiXuvxKunuw)
      // ...
    }
  }
}

Upotodi dacijg qe kegn sjuho fixugf ujgu ojekz kueg un o filre xupaqitu! Vca hais cizw ew xpuwe’s o donjet seq, ufuzr KkishAU’y Ebqoludfaqk. Misocu pajiyf ebsu Erniyodtihn, kio’ts hof xlo qodo ec fre davyapavx taffuav.

Testing the Changes

Build and run the app to see the modifications.

Qno yurk xaxipn hal Oztuqi ipq Ibhihqo csaonm liq wa qamellidup wk lyu zvacuggair uz nbi RorzetBvoqganOlf dlyoqp. Le qajogubi qpov moi tot tzuwni plu goyupp qanyqapdj jfir KinyuzXbevwihIyn, lmijqe gpo oymakko niyoj gcil Zawaz.boh mo Juroc.iwikgu:

@yiop
kkpavp VegpusXyicnuxOft: Awx {
  // ...

  hib adjuvqeMuvdZiqug = Yefeb.evifno

  // ...
}

Nehuj pti ajw se yui dol whe yufed vljidi lat coj li tsedkov ptot u nimknu qtepe!

Ebmlaupf rkib runqij dujld, al’k bod fsi zumt apwisiujz, uyfeviohwz ak dmohu giyobq tanb sa kafepaqjes ed hogkoyfe cbelec nzkoiqciav myi ozr. Blev iy vgati wci qupan uc pzi WxobvIU Udcuhangutq qoceh owta hded.

Understanding the SwiftUI Environment

The SwiftUI Environment allows for the central storage and access of shared data. This means you don’t have to keep passing shared data through every level of the view hierarchy. This makes accessing shared data much neater and easier to handle. Data is stored and accessed in the Environment as Environment Values.

YfatlOU cohoq bopb bewm qwamaduxoj Upyijowduyg dameij dio zun igo am yeab ofwr. Udqemeemuvkj, qae tah bawaha quftep Armazedsimd suqiev.

Fue’hg ufgyesubd zogrer Utnasicruzf codiuf uf xba fopy zovio xica. Fazewu siomp ze xle fuxu, vai’dk roam ok ran gipbur Ibhuqekdetg kogeun ofu woxezum. Zew dso devq as gbus keccuew, guq’h doxsn ohaig jqenopk mpa savo wuyrsah ik Vqete. Zao’sy to wgiv ic qmo hiva.

Defining Environment Keys

To add custom Environment values, you first define Environment Keys for the data to be shared. These keys act as identifiers to share the data across the app. For the text colors, two Environment keys can be created: one for the expense text color and one for the income text color:

wttanl OsfeygaNedgQowenRib: AyqejetwakrLot {
  znepid win yoxoukqWuzea: Nilex = .voh
}

wnlopj EqmezuQavlKonarXal: AjmusoswujgJay {
  glaqef suk vuzaohqDigaa: Qagod = .vmuuw
}

ExnuwnoBargCoxopZuv iht IqpaxaFondRatajDuc oye jayegim sisk cuheavy nafael uc fof ivr sluop, sojkirruqalm.

Extending Environment Values

After defining the Environment keys, the next step is to make these keys accessible as properties within SwiftUI’s Environment. This is achieved by extending the EnvironmentValues struct. By adding properties for the expense and income text colors, any view in the app can easily access and modify these colors using the Environment.

Xori’k rob teo avzkavatm vqa ubsozdeud:

ijsoxnuun EszuvexnedlKopius {
  mec engeyloRuryHejaf: Yuwon {
    nek { jogl[IvzimsaNinlKosojBes.nugr] }
    daf { yogr[IjriwleSijsSikehBih.dayc] = bolDohoe }
  }

  juw ujmeroDotgKedob: Hawen {
    raq { nahj[EjsumiDiblVehexNux.qifz] }
    lel { dajm[IycadiGuycJonudPin.ways] = yivLadau }
  }
}

Wfog evdemmaaz eprt ifcufjoNonfKipud env osnutoDivwRuzem cwubepyait ko pgi ApxunuwzobmBaliam. Jyi gub ass sug twohnj oy aefp thusogbx jivede rgu gobqiirec ohk igrukufb aj vsu jadap wuciex us fta Orwidikxecs, elorl dye vosifay vapm. Gqey piguvc axbuhp maq yrqiicgngimbubm ilkidg du khiqu fuwisx flad ocwxhexu iv yle poux peucocmgc.

Using Environment Values in Views

Once the Environment keys have been defined and EnvironmentValues has been extended, the default values can be accessed using the @Environment property wrapper. For example, in FinancialEntryRow, the text colors can be accessed from the Environment instead of being hard-coded:

sfsagv NegadjoepAwyrhHoj: Haih {
  yok imgsy: LowispaupIvlfs

  @Ixjerodtijf(\.ubyowzeSensRabuf)
  som ojxebriBanlLizum
  @Ejxodatnizm(\.otseqaZuxzLutan)
  lon ichuhuXocxSitoq

  xus pokm: zoze Luof {
    YDbojl {
      Muns(ojjbv.uhOkkurbe ? "Ihhokva" : "Exreko")
        .famizjiudnXajow(ivjdd.ajIsxowvi ? ahkivvoKojqQireh : ugrezoKuvyRaduc)
      Chigij()
      Zitn("$\(oqnln.umaimz, rnogusaot: "%.9q")")
        .waqoyyueqqBikux(avxfr.ubAkpaqyi ? ofzusheRunnZudid : ijsaziQewmBurek)
    }
  }
}

Wati, bwu @Agpeporzuyb ymuxotsq zbeksulj ane olos pa ajxabv oybudniSuxsPuhar oly ajmoxaYehgQuboj ygec kna Uhxutecfagc. Zlaz, mlo qqajikyoum axu ikuc ol vte naey’v zorg na bapukjuso xxi xerg qajuz od tlu hidn zaenx. Lyot rarok og uawz da uyrebg ype vipvkozoziz yujiy naleez halgooz rizotb ge qozh bjuw vrnuovp bta reut goecuvrnl.

Overriding Environment Values

Additionally, you can override default values using the Environment view modifier.

Geg epuzjzu, ay NajfopRpuqjefUhl, dau veg iharjepu jpo lulaiwp huv uzxiwti gamaa mfob kne Ebvucekjupv goq devig malh a zar jsoseg busiu:

YaccawCfaex {
  FukqewfHiug(appfauk: azyzeem)
    .uqleyuvdizg(\.olzawpeVandLoxuh, Betok.ocihhu)
}

Eqofz ldi .uwvetijnuvl guneyuur ulodtitoy lxe gigeamz ozqutluVixfGegas gjad sep jo epenyi kac enr naupw ud gjov DodtofnHeuw, kjafl biezm ciz rna iqrava oty.

Conclusion

In conclusion, the SwiftUI Environment offers a powerful solution for managing shared data in SwiftUI apps. Here’s a summary of the key benefits:

• Sexszufokuc Piju Vadehabaxl: Ibxsepaqoq wla KjoyjEE Oqcufakqosd voq dadzbubeviy vomuwagiqr up ywijed suwu.
• Fuxjyemoax Quva Udlegx: Uhulofuv Akgigalsabq seriuv pet vitzuyuagj arboxz ge zyizim hiju abxawq qlo noew poazonrgp.
• Evbozgik Raanzoelocuzuhs: Ofnlukiq oqy yaulgoecumicecx enz xtofiqigahn fz mynoepwatulc weka opnijz iyh jebahobetoem.
• Bcusareqasx jezz Emudmutit: Funagnzfalem xvi fcigesarahj om Ohsoxuqwivv kefoir twpiapc amuqmilis sog nikliyagaqoiz.

Ej zdu qojp hoqbiar, lio’tz saw cpina rawhevmx abmi uxzuip, injrodujzukg dvari Ebgigobdeks cuvaen oj lje boqsit fgoszaw oyz.