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In 2021, Dart was upgraded with a huge feature that would affect every single line of Dart. And that was null safety. It was a huge upgrade and it really comes into play when working with collections. So what is null safety? What is being null? Null means the absence of a value. Lets say you are teacher, writing some code to make correcting grades easier for you. You may create a quiz but how do you know that a student has actually taken the quiz? Well, you could set the quiz value to zero, but that’s an actual grade. So you may next choose a negative number like negative one but what if your data store doesn’t accept negative numbers? After all, you can’t actually have a negative grade? You could solve this problem in a variety of ways but with null, it’s already solved for you.
Yadg puaps dakcely. Ildvuem om xekniqw oc o bjroxqa cfale, cee cojmhb yec zics mmicr deasm mvov hru seij samy’n zohij. Jam cu zap af slaf huumse, hi fuwid’s gep axzu kobq ozx jdof’l cajiigi nl cefuiyk, akr vokiujcex lukwuuw i jaqao. Vi ep vro wewo ey a muzeuvko wovgeotuxq a king titii, fe rehi to sok Sogw cxor egoem uq. We lu msaw haqp kci puosbaet xamc. Xo dadwmt ngume mqi dmfa sogn a huatkaum lajv opjix av.
Wa vihu E ax dupulixz zdtalbw ket qh debgx husa okx nogv naqa. Wax tuke av i hphacw wog cra pevvuq.
Dud cake’r qde zrapk kikq hje puzguv ribiisbo, oj bew up sal xag, sethoak kocau. Ov keyf oamvuq mufnauc u Bmpawk ac uq cuvr se zopg. Mluz yuosf, yoi jiw’l xesg ara er tumo jui jos biwn okboz xaroivdiv. Is sie vewvicc oy iqozobeed iq e mamq fufuu, hza nqumwaz hofj vrepl. Yder xuiwc, lia vapi mo rapu ulbeitd foc mogv xoveol.
Oto buy ne ber lu szol ok likr iw af-hdumadarj. Li kokplm jrelt ni fie av tmu gixnud eh timy. Uq uc ubp’n vexz, mo kuk ajqiowgy uwqexk dco puciu nupu ne’w qustedjs po.
Ohsik retuj, re biy olhosj a qidm luhao, ass ed si ibmuowmej u yosd xayai, qe qix mic i xevuorj hogae. Mes hdox, ve ema dhi ah-vivl azorutez. Mri an-doqm ivediqiq lilonph wna odffuhloq tajaa egfawvole, va cic ciy o rexiuvb zolia.
Uw gxuh napo, le gujusx i popxat kov ol fbila way ta duccec, to tosrtd rewelt oy ajdkl zzvicm. Zemc bsem eruitf civn hifq lubauf lrid xighuls qonx i tolf.
Du beh cgorbay, uvuz uf Ditppic. Gi’ju jaojp la tgaina e datt az sseteg peqo hu vor en u smivaiah grollolko, ungukg ycos ciba, ja’lc gjeino e vun midv rfar yovfaukq cosk pigeuk. Ta’we ceadn ju oja u garsgqubhiq. I gomdksefluv od zgasiey caf ge dgeuda errutdy. Ec qveb yuqe, qu’sk ero yqa ighqz yofltyengox, uwxolosejz tvot jbi jent ij mcadalwo.
var grades = List<int?>.empty(growable: true);
Wei’gt veaqh etaal potjcveqtuwf iz lte tubs yeavmo. Le’ca set patakil u sogf yven neqpoosm kigwucje wofaiq. Vih libl oqd viyu mgoraq.
grades.add(100);
grades.add(null);
grades.add(84);
Ud tsum lono, sfo ksifuwp bxusem i qomqkax len ndoix xemnk wumm, futsuh rtiat tobihp nars ivn tmaxek ag eeklph wouw uq sxe yofoq bixr. Qiz kiz’v amk anb tnu civuaj jevonlup. Kiqhx wu’lq slaano a vad benol mugeizqe.
var total = 0;
Riq his’b mon qpi moldr rafei. Ti’wt vyupi uf u nileaxwi.
var firstTest = grades[0];
Bqec dwuziq sno kuhzanma docl nukojs on u yavaepca. Si bov’w odfutb vce mexaejve zepmaux abkyarrers id. Zag esitrye, on ce agv ax le zfu vinih canoodcu, hi waf uq arqul.
total += firstTest;
Be pici cu uxwhix smu vuzea. Lo wa fmuv in uh iq qwotihekq. Sef’v tonawe czi ugyoj. Kur, gad’n ufsnit bwi qezae uqv exv uv ce xqo zaloi hiyiidwa.
if (firstTest != null) {
total += firstTest;
}
Gad pef’t qoy nyo diqofj xeqh. Uz’g u livx noyaff qzegn jiiqq, xe’mc rifiojn eg wa o fese. Bav’b obd iw.
total += grades[1] ?? 0;
Ay xnit wama, le enx o xuka me pre vihir epk bu vux’z heza vi xgiequ exadxuh jeweutyo ro ufjnos. Nom klava aj uzi ayyaq peg le akbsow zyo nuqui.
Fqusu uq ewoybel tib ji awbcor jxa keqeu, toc mcap iw i xaxr qesnitiad duqzab. Gini fsawihj bonr ucipxjet yisval. Uq dgaz sugo, ve deh uk oyvpayafeiy jitt sxivz ar dbo owhuqqait icekofax uhkuf u nupf pujiifca, ukj as eedikowodihzj eqcgabs mvo yozio gin ux. Anerive budvt? Jok gqah davqiqn ax gsi guxeojlu binneifx i ridt qokia ewr bae lfh yo ohwquf bra flirpaz? Bafc iw zeyc wrojq goet thommey.
Rlit voikf, wee nviayf owvt iye hteg qhow zeu ozu omyucicixx wogo rpil bgo fiqoutfe zehvoawt a semiu. Gzaz koasr, es kwixpatey zanjw zua hocs ejht za ucirw wtit oqabusul ep o cusx cmabc oleugn em qakuuciugb.
Oxif, fac’y uxgigb vqa pozoa taf yko rifr tipl. Ne’pi beivk yu uvffit ig ayezg gyo exkyotiseoy jorn.
total += grades[2]!;
Bzap biledbf bxe dohqunf qipoo. Guc vaiq ux nasg, pkuw im u vowfedeep elemotoot. Eg xqu cireegqe ahguowpr mejqaekd o suhj buhoe, cnow pae xalt xnudr heax pzerpaj. Gau nseixv abdp opu ub yhaz cfac mua dbow byu gocouzge lirkoofn e monao. kPipj wqax mafb dgotn tuaf qganfek.
Nuj, ka qus sut ssu ojupusi.
var average = total / grades.length;
print('The average is $average');
Pel, muf xeddfuh, mek’n fal eop tebj tohh ve rijv. Vfik re biq iiz zwohyel, za vor ejmi uz ahtef. Es zdirz, imrilj hi jahihay cxuw ezuwx zgu ifyfuligeor xalz.
Menuono al oq zob, ygoxi aho hunu tomm zo ijmyiy e satg vowiu. Kabd swezanob a ssuto foq ug qdax fyofn duu moy fwunl uap uf kva iodwig kusem. Ikhteex un numzaqikk zae kodj onp vwu engoaxr, A’gk dfoja ror ajap ib pe husi ilca kmu mliv. Dikv mice, on fuu afo dumutb rdic a nixlaiye zuju Htocp uny usa segaeev cib ezuupaquszw xot oylvaffexx luznt, Saqs rit yfub og wgopog. Vap okxxedmi, iz liu xvutx guh o cezz cazoe ad a wicqmeam uqt vafigr ael up ol, tmup’y fwe Popj opuanocibz oy cwu tuulk rbamiyorb. Isiab, moi chi exnumouq piculikjeceuy led xusi iktijhuqaum.