Upgrade to Pro
— share decks privately, control downloads, hide ads and more …
Speaker Deck
Features
Speaker Deck
PRO
Sign in
Sign up for free
Search
Search
useRefについて調べてみた
Search
Kazuki Shibata
September 04, 2019
Technology
1
140
useRefについて調べてみた
2019.09.04 React LT会の発表資料です。
https://informetis.connpass.com/event/142183/
Kazuki Shibata
September 04, 2019
Tweet
Share
More Decks by Kazuki Shibata
See All by Kazuki Shibata
microCMSでif文を作る
shibe97
1
1.1k
SvelteKitでJamstackを試す
shibe97
1
1.1k
フロントエンドのトレンド〜サーバーレスSPA、Jamstack〜
shibe97
16
4.8k
Jamstack × PWA におけるキャッシュ戦略
shibe97
3
1.2k
CSR / SSR / SSGの動向2020
shibe97
2
1.5k
Jamstack×microCMS 実装編
shibe97
4
900
SentryでSPAのエラーログを収集する
shibe97
1
1.6k
フロントエンドエンジニアのキャリアパス
shibe97
9
3.7k
Containerどこに置く?
shibe97
1
1.9k
Other Decks in Technology
See All in Technology
CDKのコードレビューを楽にするパッケージcdk-mentorを作ってみた/cdk-mentor
tomoki10
0
210
AWS re:Invent 2024 re:Cap Taipei (for Developer): New Launches that facilitate Developer Workflow and Continuous Innovation
dwchiang
0
170
[JSAC 2025 LT] Introduction to MITRE ATT&CK utilization tools by multiple LLM agents and RAG
4su_para
1
110
20250116_自部署内でAmazon Nova体験会をやってみた話
riz3f7
1
110
[IBM TechXchange Dojo]Watson Discoveryとwatsonx.aiでRAGを実現!事例のご紹介+座学②
siyuanzh09
0
120
メールヘッダーを見てみよう
hinono
0
120
KMP with Crashlytics
sansantech
PRO
0
250
DMMブックスへのTipKit導入
ttyi2
1
110
いま現場PMのあなたが、 経営と向き合うPMになるために 必要なこと、腹をくくること
hiro93n
9
7.9k
デジタルアイデンティティ人材育成推進ワーキンググループ 翻訳サブワーキンググループ 活動報告 / 20250114-OIDF-J-EduWG-TranslationSWG
oidfj
0
560
タイミーのデータ活用を支えるdbt Cloud導入とこれから
ttccddtoki
1
300
AWSサービスアップデート 2024/12 Part3
nrinetcom
PRO
0
150
Featured
See All Featured
The Power of CSS Pseudo Elements
geoffreycrofte
74
5.4k
Building Better People: How to give real-time feedback that sticks.
wjessup
366
19k
個人開発の失敗を避けるイケてる考え方 / tips for indie hackers
panda_program
98
18k
How To Stay Up To Date on Web Technology
chriscoyier
790
250k
Thoughts on Productivity
jonyablonski
68
4.4k
Build your cross-platform service in a week with App Engine
jlugia
229
18k
Six Lessons from altMBA
skipperchong
27
3.6k
Gamification - CAS2011
davidbonilla
80
5.1k
Documentation Writing (for coders)
carmenintech
67
4.5k
GitHub's CSS Performance
jonrohan
1030
460k
What's in a price? How to price your products and services
michaelherold
244
12k
Facilitating Awesome Meetings
lara
51
6.2k
Transcript
useRefʹ͍ͭͯௐͯΈͨ @shibe97 2019.9.4 React LTձ
ࣲా ف ΥϯλגࣜձࣾͰmicroCMSͱ͍͏ϔουϨεCMSΛ ࡞͍ͬͯ·͢ɻ ීஈReact͍Ͱɺ࠷ۙVueͪΐͬͱ৮Γ·͢ɻ @shibe97
None
ೖྗϑΥʔϜͱAPIΛඵͰ࡞Ͱ͖ΔαʔϏε
React Hooksͱ • React 16.8͔ΒՃ͞Εͨػೳ • Functional ComponentʹClass Componentͱಉ༷ͷॲཧ͕ Ͱ͖ΔΑ͏ʹՃ͞Εͨ
• stateϥΠϑαΠΫϧ૬ͷͷ
useRefͱ • DOMͷࢀরʹ͑Δ • ࠶ඳըͤ͞ͳ͍มཧ͕Ͱ͖Δ
DOMͷࢀরʹ͑ΔʢެࣜྫΑΓʣ function TextInputWithFocusButton() { const inputEl = useRef(null); const onButtonClick
= () => { // `current` points to the mounted text input element inputEl.current.focus(); }; return ( <> <input ref={inputEl} type="text" /> <button onClick={onButtonClick}>Focus the input</button> </> ); }
࠶ඳըͤ͞ͳ͍มཧ͕Ͱ͖Δ • refΦϒδΣΫτΛcurrentϓϩύςΟʹอ࣋͢Δ • ࠶ඳը࣌ɺຖճಉ͡refΦϒδΣΫτΛฦ͢ • currentʹೖͯ͠࠶ඳը͞Εͳ͍ { current: initialValue
}
useRefͷ࣮ function mountRef<T>(initialValue: T): {current: T} { const hook =
mountWorkInProgressHook(); const ref = {current: initialValue}; if (__DEV__) { Object.seal(ref); } hook.memoizedState = ref; return ref; } function updateRef<T>(initialValue: T): {current: T} { const hook = updateWorkInProgressHook(); return hook.memoizedState; } ϝϞϦ্ͷΛຖճฦ͚ͩ͢ ϝϞϦ্ͰΦϒδΣΫτΛอ࣋ currentϓϩύςΟʹΛอ࣋
͜ͷΈΛར༻Ͱ͖ΔྫͬͯͳΜͩΖ͏
DOMͩʂ
inputཁૉͷྫ: useState function TextInput() { const [ text, setText ]
= useState(‘’); const onChange = useCallback(e => { setText(e.target.value); }; return ( <input onChange={onChange} type="text" /> ); } ςΩετΛมߋ͢Δͨͼʹඳը͞ΕΔ
inputཁૉͷྫ: useRefʢcurrentࢦఆʣ function TextInput() { const { current } =
useRef(null); const onChange = useCallback(e => { current = e.target.value; }); return ( <input onChange={onChange} type="text" /> ); } ςΩετΛมߋͯ͠࠶ඳը͞Εͳ͍
͋ΕɺͰ͜Εͬͯɾɾɾ
inputཁૉͷྫ: useRefʢDOMࢀরʣ function TextInput() { const inputEl = useRef(null); return
( <input ref={inputEl} type="text" /> ); } ͪΖΜ͜ͷํ๏࠶ඳը͞Εͳ͍
·ͱΊ • useRefΛอ࣋Ͱ͖Δ্ʹɺมߋͯ͠࠶ඳը͞Εͳ͍ • inputཁૉʹuseStateΑΓuseRefͷํ͕ύϑΥʔϚϯεྑ͍ • ͪΖΜControlled Componentʹ͍ͨ͠߹useStateʹ͢Δ ඞཁ͋Γ
͓·͚
useRefΦϒδΣΫτΛࢀর͍ͯ͠Δ͔Β ෦ϓϩύςΟมߋͨ͠ͱ͜ΖͰ࠶ඳը͞Εͳ͍ΜͩΖ͏
Α͠ɺLTωλ͜ΕͰ͍͜͏ʂ
useRefͷ࣮ function mountRef<T>(initialValue: T): {current: T} { const hook =
mountWorkInProgressHook(); const ref = {current: initialValue}; if (__DEV__) { Object.seal(ref); } hook.memoizedState = ref; return ref; } function updateRef<T>(initialValue: T): {current: T} { const hook = updateWorkInProgressHook(); return hook.memoizedState; } ϝϞϦ্ͷΛຖճฦ͚ͩ͢ ϝϞϦ্ͰΦϒδΣΫτΛอ࣋ currentϓϩύςΟʹΛอ࣋
·ͬͨؔ͘ͳ͔ͬͨ
Thanks :) @shibe97