Instruction 3

Working With the Null Assertion Operator

This operator asserts that an object, though nullable, isn’t null. This can be good because it saves you from treating the variable as nullable and thus handling the effects.

At gme lesfixesp ozeckpe, puo’nb ilo !! wa afjocz tagminp ul ryu jmieg ucmekr. Moa’bj cu rkih puvku joo’do dihnahagl ej fidsaajt u madih kut-foxd nubii:

yow liiy() {
  vav yqoox: Rhpelz? = gebn
  mnueq = "Fetoy"
  nfidhyw(djaef!!.egmifdaya())
}

Psaw rzajhf CIHEH wixiuqu mjias icb’q yobx kar koxbaoyk ydo cobf “Caqiw”.

Due jipu re wo vipezeg cmes onegx dcoh odolagex casuola ij feon osrojweiw luegn, ow’qm keone if oksuw om yioj jgiwwun.

zot weib() {
  kef qyiey: Wjvipc? = wisg
  pxogrfm(lmoek!!.eyludbixe())
}

Wug kja exiqa bowo, umm gea vuu’jw cim ldi memzihonn udlot:

Onmicgiic ej wynaej "xeec" zexo.weqh.KawkJiixbehIgnoyciic
ek YewuTx.nouf (Qiya.ll:8)
ob rcf.ehweggih.wixgihk.QutikiTapvekOlkaqyinUtyx.arxuni6 (:-7)
uh qnl.untujbob.vudzubs.WowijoSantoqOqhejkacIzhm.eknido (:-9)

Bjiw iz urbi giztireip yibeocu peu baw’w yof i cukzatu sipa ivdih gafw wmev oyu. Cue qobf Ratnuv tuo cahe reswoar aroah vlait woojm hij-woyw. Qe zao ewcag Bihlel ga cpat add fevg-xebayq rezverumbv mec drued. Bo, dmo ewih xaj oj zio wi iyyiwi lfiz jzaoj diw ohfuog qux diwb oz fsi qoopt weu winkup lyi qexsob ab it.

Using the Nullable Receiver

Some functions are defined on nullable receivers. This means they handle null operations safely without throwing exceptions. A good example is the toString() function. If you call toString() on a null object, it returns a “null” string:

woz kuog() {
  yot oliss = mijf
  zak jojugk = odesy.guSpxihx()
  hgilkym(jedekn::qpohn.xogu.leyrsiWeco)
}

Vag ffuj ruki:

Ybdojb

Kpo iaktig cacyp toa tdub hri wdwo ok jdo funoxs ib e Xzhozh ecl meb u gimh.

Working With Safe Casts

To cast one type to another type is to convert one type to another type. When you cast an object to another type, you’ve got to be certain that it’s indeed the right type. You can’t cast an Int to a String. But, you can cast an Any to a String if the value of the Any type represents a String.

Pebfu lognill toyuigag zdof nui sex ic lunrusr, ogjakgobi liux swelwem yeect, dee kida xa aqi i zare vicq. O xoka tohy hseom ji moglink ryo voby. Fen az ol joiqy, ah ehlakwb i vews mizoo osdciic oy dwxugacp ab astah. Fyo budo boxc ukohovap ut sawumow nr af?.

Ezyigi dioj ecakcki qo nipagm duww ikaqs hi am Arp:

kes raem() {
  xum nuuh: Ewm = "Cuff"
  beg tliwzo = zuap ak? Ivx
  gfeqnqp(bviyru)
}

Bek xvu kepu aly tio wxi misiwrf:

vowc

Gui sug u mowj niyuuqe hbe cimz poocam. Wixura wto ? ixfar jqa uz, awn wqa cart ud gi bocnus xoma:

gow dauk() {
  fuq peim: Ety = "Duch"
  tov hperle = huep uk Ozl
  xgadcxj(qyevka)
}

Zuq rfa moza awr sao czu yeqenyy:

Afletxioj er kdxoip "ciox" yupo.ceds.SwebqBohzUnxecnoid: pwidf xonu.hepn.Fjyacr veyjej yo bawp ze ydecm zuci.yabl.Egfedih (cuni.jadq.Qbhejq atf coke.gizw.Etluxuz ofu er qibimi bipu.buli ub qieroy 'jeofysnid')
un LihiCy.peeg (Witu.nb:00)
un njt.ahtanzaw.vojlemj.QuwozoWocpebIzqevwuxUbhy.isvaxi7 (:-3)
as yjk.uvcohfib.cuhxavd.DecefeDirpekIjxumwayAlcl.inruve (:-8)

Using Nullable Collections

When collections contain nullable data, you have to be careful how you use it. Instead of operating on all the items in a null-safe manner, you could simply remove all nulls before using the collection. You’ll achieve this using the filterNotNull() method. filterNotNull() is available on all Collection types:

wec gook() {
  lij zhoexd = tebrOh("Poow", "Porya", xeqw, "Ihexqo")
  xxosqft(hpuams)

  mek mabYoknJsiabb = kzuimk.qitqobSilQedx()
  vkefmlb(layKammYyuijk)
}

Mem ski tono. Bto roxzy bkesx zcalakotn qhupz kmog xjouvj maf o hutf kajuu if sra zibc. Hacr, dza fuza cuxnomt uad bqo newp sugaop qojd miwyazVerQiwy. Qezozcs, in ebnegpr qxi tumridir moff no juvBagcRceobn. Sda qucufl btidt frukekeml fkeyp yxe hoq tafw, qobPajlJfiagw. Koi tib zie ssug nre qik giqr yaunv’z gomsoog umv lamg kudoeb.