Video: Dab tsi yog kev xaiv khi Swift?
2024 Tus sau: Lynn Donovan | [email protected]. Kawg hloov kho: 2023-12-15 23:47
Koj siv xaiv los khi mus xyuas seb cov xaiv tau muaj tus nqi lossis tsis. Yog hais tias nws muaj ib tug nqi, unwrap nws thiab muab tso rau hauv ib ntus tas li los yog txawv txav.
Tsis tas li ntawd kom paub yog, dab tsi yog kev xaiv chaining thiab xaiv kev khi hauv Swift?
Cov txheej txheem ntawm querying, hu rau cov khoom, subscripts thiab cov txheej txheem ntawm ib xaiv tau uas tej zaum yuav yog 'nil' yog txhais raws li xaiv chaining . Kev xaiv chaining rov qab ob qhov tseem ceeb - yog tias xaiv tau muaj 'tus nqi' ces hu rau nws cov khoom muaj feem xyuam, txoj hauv kev thiab cov ntawv sau rov qab muaj nuj nqis.
Tsis tas li ntawd, txhais li cas hauv Swift? Swift version: 5.1. Swift siv cov cim exclamation los qhia ob qho tib si quab yuam unwrapping ntawm kev xaiv thiab meej meej unwrapped optionals.
Ib tug kuj nug, yuav ua li cas kuv unwrap xaiv Swift?
Koj ua tau tshem tawm kev xaiv nyob rau hauv peb-thiab-ib-ib nrab txoj kev: Nrog quab yuam unwrapping , siv yog tias [ xaiv tau ] != nil thiab [ xaiv tau ]! Nrog xaiv tau kev khi, siv yog cia [tsis yog- xaiv tau ] = [ xaiv tau ] {
Dab tsi yog cov ntaub ntawv khi hauv Swift?
Cov ntaub ntawv khi . UI cov ntaub ntawv khi yog software tsim qauv kom yooj yim txhim kho cov ntawv thov GUI. UI cov ntaub ntawv khi khi cov ntsiab lus UI rau ib daim ntawv thov sau qauv. Feem ntau lub moj khaum siv tus qauv Observer raws li hauv qab kev khi tshuab.
Pom zoo:
Dab tsi yog qhov sib txawv loj ntawm kev txheeb xyuas qhov yuam kev thiab kev kho cov lej yuam kev?
Ob qhov kev tshawb nrhiav qhov yuam kev thiab kev kho qhov yuam kev yuav tsum muaj qee qhov ntawm cov ntaub ntawv rov qab xa mus nrog cov ntaub ntawv tiag tiag; kev kho yuav tsum muaj ntau tshaj li kev tshawb nrhiav. Parity bits yog ib txoj hauv kev yooj yim rau kev tshawb nrhiav qhov yuam kev. Ib qho parity me ntsis yog ib qho ntxiv me ntsis xa nrog cov ntaub ntawv uas tsuas yog 1-ntsis suav ntawm cov ntaub ntawv
Kev xaiv tsa luv luv thiab kev xaiv tsa ntev yog dab tsi?
Kev xaiv tsa yog cov txheej txheem los ntawm cov neeg thov kev pabcuam rau cov ntaub ntawv tshiab tsis tu ncua. Hauv cov ntsiab lus yooj yim, Shortpolling yog AJAX-raws li timer uas hu rau ntawm qhov ncua sij hawm ncua sij hawm ntev yog raws li Comet (piv txwv li server yuav xa cov ntaub ntawv rau tus neeg siv khoom thaum lub server tshwm sim nrog nodelay)
Kuv yuav ua li cas xaiv cov kev xaiv hauv Word?
Xaiv cov ntsiab lus tswj, thiab tom qab ntawd xaiv Properties. Txhawm rau tsim ib daim ntawv teev cov kev xaiv, xaiv Ntxiv rau hauv Drop-Down List Properties. Ntaus ib qho kev xaiv hauv Lub Npe, xws li Yog, Tsis yog, lossis Tej zaum. Rov ua cov kauj ruam no kom txog thaum tag nrho cov kev xaiv nyob rau hauv daim ntawv teev npe
Kev xaiv chaining thiab xaiv kev khi yog dab tsi?
Optional binding khaws cov khoom koj tab tom khi rau hauv qhov sib txawv. Hauv qhov no, nws yog navigationController. Ntawm qhov tod tes, xaiv chaining tsis muab tus nqi ntawm sab laug rau hauv qhov sib txawv
Dab tsi yog qhov kev txwv kev ncaj ncees piav qhia txog kev ncaj ncees lossis kev txwv txawv teb chaws?
Kev lees paub ncaj ncees xav kom tus yuam sij txawv teb chaws yuav tsum muaj tus yuam sij tseem ceeb sib xws lossis nws yuav tsum yog null. Qhov kev txwv no tau teev tseg ntawm ob lub rooj (niam txiv thiab menyuam); nws tuav cov ntawv xov xwm ntawm kab hauv cov rooj no. Nws txhais tau hais tias kev siv los ntawm kab hauv ib lub rooj mus rau lwm lub rooj yuav tsum siv tau