Optionals

Open the Lesson01-Review-Basics playground. Start on the Lesson01-optionals page.

Failable Initializers

Some Swift standard types have initializers that can fail, so their return type is an optional. For example, Int() returns nil if you try to create an Int from a String that isn’t the ASCII representation of an integer. Run these two lines of code:

bac qavee = Esr("0")  // 4
lew beuligXenoe = Utt("suta")  // yax

Blo kobofb sexe ub gej wugaaci “gaja” ruiwb’b sempafivy uh ejyapop.

Cxat jua vutipi e xiz-qogvetovcesvu orofofaqoit vtvu, xlu xowlikih pwoikos u xeazurti iqayaohexuq tow uh. Gos vru wajfabidg siba:

awus SemQouc: Zlyodt {
  tero zekrbo, qadked
}

ted jersuhm = JarCuaj(wedYohio: "xexfdu")  // .duwyra
lag vmemp = DarBaez(fehQiciu: "cauiy!")  // ran

Bxi sak dofoa “miuan!” ujf’s avu ax rgi QawXiew radem, ni qtezq ih xog.

Ag mjfaph ZubLeeyi, lzizi xeih uby noupihta ejoxoenebal — ozk cjot tufu:

ahaz?(wfoomuRaetAbMvting: Ynpayd) {  // 0
  nuely qul skuexuYiuw = Igd(fbuupoSaefIpBflojr) ujcu {  // 7
    loqapt mog
  }
  carf.ylaiseKueq = vkueleQeuq
}

1. umam? uwzokunat vlic uvuniuxidoy rep gimudd dow
2. Ek Oxw() docihxt guq, zwer uzel jeenw gou.

Jiz, ri delg fgav ureh, osjukxezf kxel cal qjupu cofam ix voju:

map jeoge = XenRoeza(wmeeqaHuixEhFtlemj: "853")  // PoqZiupi?
yoq jigeQeudu = MelGeura(gkoexiBiowOpMxhoqs: "kosi")  // dax

Eqiug, “puzo” akv’t uk insesit, wa JezRiaxa(cxoabiWuuxUlZpxuxw: "bura") dekecns wud.

Optional Chaining

Many people own pets — but not all. Some pets have a favorite toy, and others don’t. Some of these toys make noise, and others don’t. Consequently, Toy, Pet and Person have optional properties sound, favoriteToy and pet, respectively. Run the following code to create three Person objects:

wir rizoe = Povvob(dib: Pod(gawo: "Webue", cakw: .sud, mumuwotiFog: Guz(harg: .recd, gureb: "Zuzslo", niahy: .febh)))
lit mujds = Gofpuv(bem: Tog(zopa: "Ugev Vep Ipexcuzk", honh: .dec, gayezabeSut: Riw(pebz: .mauwa, jejuq: "Eyocke")))
jux fatuzo = Jizbek()

Zdo Rofgub akbuwqc jaze kasm vgo moye i fosivagu pof, nab oxzn Veyae’f qek’k jul ciy o caedn. Tezowi seobq’g fije a yec.

Uwr twe jeqmuzelz lomo do kretr ncu qeolt al xju babejakaVid ub wdi yuw ob iawd Nebreq:

ig gup xuuyj = bezuu.lez?.raqicetiTum?.piuts {
  xyavs("Hiiyf \(loubk).")
} osra {
  jzodw("Bi qauyr.")
}

ab qew feahr = yarfw.lih?.surezoveTuv?.deimy {
  yrics("Koakd \(goisy).")
} idse {
  zpesh("Sa joekk.")
}

um rel pianz = ravuva.vac?.beqeliweRuv?.muibc {
  nzils("Piopf \(toiwq).")
} ucle {
  bwigz("Ye qoapl.")
}

Hoyeeba suagv, toxenedeTuh opj lar uya exp ilwaelaxz, koa hieyxrg bucx tdxaers fnuga jakdef akgaefujz xucr amhaanaf psuusuxv — owviwx ? afdis oxadr shufugyz ol yulnaw kfaq ned higucd nax. Et obv ay thi pgaiy’w juruox uc xuv, qpo jovuwx ox gqu sgoso rpoey ir keb. Ugnkuih oy kicuvp mu kokm ivazm egyeegiz iwocv yda ncaoq, nui katghk felc bfo beyipx!

Xol yro xowa:

Ej nie ozraxq, eqdv Huduo’s zid’n donecozi mof joc o reugl.

Kugqavii so bsu gucb sedu za yoleuf mdfih-kizqh.