値オブジェクト / Value Object

フロントエンド百物語で発表した資料です。

Transcript

1. ஋ΦϒδΣΫ
   τ
   "VH ϑϩϯ
   τΤϯ
   υඦ෺ޠ
   

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2. ஋ΦϒδΣΫ
   τͱ͸
   w %%%
   ʢυϝΠϯۦಈઃܭʣ
   Ͱड़΂ΒΕΔ֓೦
   w +BWB4DSJQUʹ͸TUSJOH OVNCFS CPPMFBOͱ͍͏
   ϓϦ
   ϛςΟ
   ϒܕ͕͋Δ
   w TUSJOH OVNCFSΛ5ZQF4DSJQUͰͦͷ··ѻΘͣ

   ஋ΦϒδΣΫ
   τͱͯ͠ఆٛ͢Δ͜ͱͰɺ
   ༷ʑͳ஋ΛࣝผՄೳʹ͢Δ
   

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3. ࣮ࡍͷҊ݅Ͱͷྫ
   w "2018/8"ͱ͍͏stringΛѻΘͣʹYearMonthܕͱ͢Δ
   w "-0900"ͱ͍͏stringΛѻΘͣʹTimeZoneܕͱ͢Δ
   w 1, 2, 3ͱ͍͏numberͰ͸ͳ͘UserIdܕͱ͢Δ
   w Observable<[number, string, number, number]>ͩͱҙຯෆ໌͕ͩ

   Observable<[UserId, TimeZone, PageNumber, DisplayCount]>

   ͱఆٛͰ͖Δ
   

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4. ࣮૷ྫ
   export abstract class Value {
   constructor(protected value: T) {
   //
   }
   toString(): string {
   return this.value.toString();
   }
   valueOf(): T {
   return this.value;
   }
   eq(other: Value): boolean {
   return this.value === other.value;
   }
   }
   

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5. export class TimeZone extends StringValue {
   TimeZone: ProhibitDuckTyping;
   static UTC(): TimeZone {
   return new TimeZone('+0000');
   }
   /**
   * JST ͷ৔߹ɺ -540 Λ +0900 ʹม׵͢Δɻ
   */
   static offsetToIsoTimeZone(offset: number): TimeZone {
   const min = Math.abs(offset);
   const isoTimeZone = [
   `00${Math.floor(min / 60)}`.slice(-2),
   `00${min - Math.floor(min / 60) * 60}`.slice(-2),
   ].join('');
   const sign = offset <= 0 ? '+' : '-';
   return new TimeZone(`${sign}${isoTimeZone}`);
   }
   constructor(protected value: string) {
   super(value);
   assert(/^[+-]\d{4}/.test(value), `"${value}" ͸ɺλΠϜκʔϯͷϑΥʔϚοτͰ͸͋Γ·ͤΜ`);
   }
   }
   

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6. 1SPIJCJU%VDL5ZQJOH
   w Ҋ݅಺Ͱੜ·ΕͨϫʔΫΞϥ΢ϯ
   υ
   ʢ5ZQF4DSJQUͷਖ਼ࣜͳٕज़ͷ໊শͰ͸ͳ͍ʣ
   
   w 5ZQF4DSJQU͸

   class A { value: string }ͱ

   class B { value: string }Λ

   ࠞಉͯ͠ѻ͏
   ͜ͱ͕Ͱ͖Δ
   w ߏ੒͢ΔϓϩύςΟͷ໊শͱܕͱ૊Έ߹Θ͕ͤಉ͡ͳΒ͹ಉ͡ΠϯλϑΣʔεͰ

   ͋ΔͱΈͳ͞ΕΔ
   

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7. 1SPIJCJU%VDL5ZQJOH
   w class A { value: string; A: ProhibitDuckTyping; }

   class B { value: string; B: ProhibitDuckTyping; }

   ͷΑ
   ͏ʹ͢Ε͹ϓϩύςΟ໊͕" #ͰҟͳΔͷͰผͷܕѻ͍Ͱ͖Δ
   w 1SPIJCJU%VDL5ZQJOH͸࣮࣭͸

   export type ProhibitDuckTyping = void;
   

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