{"id":3248,"date":"2020-07-13T08:52:00","date_gmt":"2020-07-13T08:52:00","guid":{"rendered":"http:\/\/the-codest.localhost\/blog\/generics-in-typescript\/"},"modified":"2026-04-24T11:39:03","modified_gmt":"2026-04-24T11:39:03","slug":"geneeriset-tyypit-typescriptissa","status":"publish","type":"post","link":"https:\/\/thecodest.co\/fi\/blog\/generics-in-typescript\/","title":{"rendered":"Yleiset tuotteet TypeScript:ss\u00e4"},"content":{"rendered":"<p>Geneerisi\u00e4 ominaisuuksia voidaan k\u00e4ytt\u00e4\u00e4 yhdess\u00e4 funktioiden (geneeristen funktioiden luominen), luokkien (geneeristen luokkien luominen) ja rajapintojen (geneeristen rajapintojen luominen) kanssa.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Perusk\u00e4ytt\u00f6<\/h2>\n\n\n\n<p>Olet luultavasti k\u00e4ytt\u00e4nyt geneerisi\u00e4 ominaisuuksia aiemmin jopa tiet\u00e4m\u00e4tt\u00e4si - yleisin geneeristen ominaisuuksien k\u00e4ytt\u00f6 on matriisin julistaminen:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code lang=\"typescript\" class=\"language-typescript\">const myArray: string[];<\/code><\/pre>\n\n\n\n<p>Se ei ole liian erikoinen ensi silm\u00e4yksell\u00e4, me vain julistaa - <code>myArray<\/code> merkkijonojen joukkona, mutta se on sama kuin yleinen ilmoitus:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code lang=\"typescript\" class=\"language-typescript\">const myArray: Array;<\/code><\/pre>\n\n\n\n<p><\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Pidet\u00e4\u00e4n asiat selkein\u00e4<\/h2>\n\n\n\n<p>Aloitetaan hyvin yksinkertaisella esimerkill\u00e4 - miten voisimme siirt\u00e4\u00e4 t\u00e4m\u00e4n vaniljaisen <a href=\"https:\/\/thecodest.co\/fi\/blog\/hire-vue-js-developers\/\">JS<\/a> toiminto <a href=\"https:\/\/thecodest.co\/fi\/dictionary\/typescript-developer\/\">TypeScript<\/a>:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code lang=\"typescript\" class=\"language-typescript\">function getPrefiledArray(filler, length) {\n    return (new Array(length)).fill(filler);\n}<\/code><\/pre>\n\n\n\n<p>T\u00e4m\u00e4 funktio palauttaa array t\u00e4ynn\u00e4 tietyn m\u00e4\u00e4r\u00e4n <code>t\u00e4yteaine<\/code>, joten <code>pituus<\/code> on <code>numero<\/code> ja koko funktio palauttaa array of <code>t\u00e4yteaine<\/code> - mutta mit\u00e4 on t\u00e4yteaine? T\u00e4ss\u00e4 vaiheessa se voi olla mit\u00e4 tahansa, joten yksi vaihtoehto on k\u00e4ytt\u00e4\u00e4 t\u00e4ytett\u00e4. <code>kaikki<\/code>:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code lang=\"typescript\" class=\"language-typescript\">function getPrefiledArray(filler: any, length: number): any[] {\n    return (new Array(length)).fill(filler);\n}<\/code><\/pre>\n\n\n\n<p>K\u00e4ytt\u00e4m\u00e4ll\u00e4 <code>kaikki<\/code> on varmasti yleinen - voimme siirt\u00e4\u00e4 kirjaimellisesti mit\u00e4 tahansa, joten m\u00e4\u00e4ritelm\u00e4n \"ty\u00f6skentely useiden tyyppien kanssa yhden tyypin sijasta\" on t\u00e4ysin katettu, mutta menet\u00e4mme yhteyden v\u00e4lill\u00e4 <code>t\u00e4yteaine<\/code> tyyppi ja paluutyyppi. T\u00e4ss\u00e4 tapauksessa haluamme palauttaa jonkin yhteisen asian, ja voimme m\u00e4\u00e4ritell\u00e4 t\u00e4m\u00e4n yhteisen asian nimenomaisesti muotoon <strong>tyyppiparametri<\/strong>:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code lang=\"typescript\" class=\"language-typescript\">function getPrefiledArray(filler: T, length: number): T[] {\n    return (new Array(pituus)).fill(filler);\n}<\/code><\/pre>\n\n\n\n<p>ja k\u00e4yt\u00e4 n\u00e4in:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code lang=\"typescript\" class=\"language-typescript\">const prefilledArray = getPrefiledArray(0, 10);<\/code><\/pre>\n\n\n\n<h2 class=\"wp-block-heading\">Yleiset rajoitukset<\/h2>\n\n\n\n<p>Tarkastellaan erilaisia, todenn\u00e4k\u00f6isesti yleisempi\u00e4 tapauksia. Miksi k\u00e4yt\u00e4mme tyyppej\u00e4 funktioissa? Minulle se on sen varmistamista, ett\u00e4 funktiolle annetuilla argumenteilla on joitakin ominaisuuksia, joiden kanssa haluan olla vuorovaikutuksessa.<\/p>\n\n\n\n<p>Yritet\u00e4\u00e4n j\u00e4lleen kerran siirt\u00e4\u00e4 yksinkertainen vanilla JS-funktio TS:\u00e4\u00e4n.<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code lang=\"typescript\" class=\"language-typescript\">funktio getLength(asia) {\n    return thing.length;\n}<\/code><\/pre>\n\n\n\n<p>Meill\u00e4 on ei-triviaali pulma - miten varmistaa, ett\u00e4 asia on <code>pituus<\/code> ominaisuutta, ja ensimm\u00e4inen ajatus voi olla tehd\u00e4 jotain sellaista kuin:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code lang=\"typescript\" class=\"language-typescript\">function getLength(thing: typeof Array):number {\n    return thing.length;\n}<\/code><\/pre>\n\n\n\n<p>ja asiayhteydest\u00e4 riippuen se saattaa olla oikein, kaiken kaikkiaan olemme hieman geneerisi\u00e4 - se toimii useiden eri tyyppisten matriisien kanssa, mutta ent\u00e4 jos emme todellakaan tied\u00e4, pit\u00e4isik\u00f6 asian olla aina matriisi - ehk\u00e4 asia on jalkapallokentt\u00e4 tai banaaninkuori? T\u00e4ll\u00f6in meid\u00e4n on ker\u00e4tt\u00e4v\u00e4 kyseisen asian yhteiset ominaisuudet konstruktioon, jolla voidaan m\u00e4\u00e4ritell\u00e4 objektin ominaisuuksia - rajapintaan:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code lang=\"typescript\" class=\"language-typescript\">rajapinta IThingWithLength {\n  length: luku;\n}<\/code><\/pre>\n\n\n\n<p>Voimme k\u00e4ytt\u00e4\u00e4 <code>IThingWithLength<\/code> rajapinta tyypin <code>asia<\/code> parametri:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code lang=\"typescript\" class=\"language-typescript\">function getLength(thing: IThingWithLength):number {\n    return thing.length;\n}<\/code><\/pre>\n\n\n\n<p>suoraan sanottuna t\u00e4ss\u00e4 yksinkertaisessa esimerkiss\u00e4 se on t\u00e4ysin kunnossa, mutta jos haluamme pit\u00e4\u00e4 t\u00e4m\u00e4n tyypin geneerisen\u00e4, emmek\u00e4 halua kohdata ensimm\u00e4isen esimerkin ongelmaa, voimme k\u00e4ytt\u00e4\u00e4 tyyppi\u00e4 <strong>Yleiset rajoitukset<\/strong>:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code lang=\"typescript\" class=\"language-typescript\">function getLength(thing: T):number {\n    return thing.length;\n}<\/code><\/pre>\n\n\n\n<p>ja k\u00e4yt\u00e4 sit\u00e4:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code lang=\"typescript\" class=\"language-typescript\">rajapinta IBananaPeel {\n  thickness: number;\n  length: number;\n}\n\nconst bananaPeel: IBananaPeel = {thickness: 0.2, length: 3.14};\ngetLength(bananaPeel);<\/code><\/pre>\n\n\n\n<p>K\u00e4ytt\u00e4m\u00e4ll\u00e4 <code>laajentaa<\/code> varmistaa, ett\u00e4 <code>T<\/code> sis\u00e4lt\u00e4\u00e4 ominaisuuksia, jotka on m\u00e4\u00e4ritelty <code>IThingWithLength<\/code>.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Yleiset luokat<\/h2>\n\n\n\n<p>T\u00e4h\u00e4n asti olemme ty\u00f6skennelleet geneeristen funktioiden parissa, mutta se ei ole ainoa paikka, jossa geneeriset funktiot loistavat, joten katsotaanpa, miten voimme sis\u00e4llytt\u00e4\u00e4 ne luokkiin.<\/p>\n\n\n\n<p>Yritet\u00e4\u00e4n ensinn\u00e4kin s\u00e4ilytt\u00e4\u00e4 banaanit banaanikori:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code lang=\"typescript\" class=\"language-typescript\">luokka Banaani {\n  constructor(\n    public length: number,\n    public color: string,\n    public ionizingRadiation: number\n  ) {}\n}\n\nclass BananaBasket {\n  private bananas: Banana[] = [];\n\n  add(banana: Banana): void { add(banana: Banana): void {\n    this.bananas.push(banaani);\n  }\n}\n\nconst bananaBasket = new BananaBasket();\nbananaBasket.add(new Banana(3.14, 'red', 10e-7));<\/code><\/pre>\n\n\n\n<p>Yritet\u00e4\u00e4n nyt luoda yleiskori, joka on tarkoitettu eri tavaroille, joilla on sama tyyppi:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code lang=\"typescript\" class=\"language-typescript\">class Basket {\n  private stuff: T[] = [];\n\n  add(asia: T): void {\n    this.stuff.push(thing);\n  }\n}\n\nconst bananaBasket = new Basket();<\/code><\/pre>\n\n\n\n<p>Ja lopuksi oletetaan, ett\u00e4 korimme on radioaktiivisten aineiden s\u00e4ili\u00f6 ja ett\u00e4 voimme varastoida vain sellaista ainetta, jossa on radioaktiivisia aineita. <code>ionisoiva s\u00e4teily<\/code> omaisuus:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code lang=\"typescript\" class=\"language-typescript\">rajapinta IRadioactive {\n  ionizingRadiation: number;\n}\n\nclass RadioactiveContainer {\n  private stuff: T[] = [];\n\n  add(asia: T): void {\n    this.stuff.push(thing);\n  }\n}<\/code><\/pre>\n\n\n\n<h2 class=\"wp-block-heading\">Yleinen k\u00e4ytt\u00f6liittym\u00e4<\/h2>\n\n\n\n<p>Lopuksi yritet\u00e4\u00e4n ker\u00e4t\u00e4 kaikki tietomme ja rakentaa radioaktiivinen imperiumi my\u00f6s k\u00e4ytt\u00e4m\u00e4ll\u00e4 Generic Interfaces -rajapintoja:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code lang=\"typescript\" class=\"language-typescript\">\/\/ M\u00e4\u00e4rit\u00e4 konttien yhteiset attribuutit\nrajapinta IRadioactive {\n  ionizingRadiation: number;\n}\n\n\n\/\/ M\u00e4\u00e4ritell\u00e4\u00e4n jotain, joka on radioaktiivinen\ninterface IBanana extends IRadioactive {\n  length: number;\n  color: string;\n}\n\n\/\/ M\u00e4\u00e4ritell\u00e4\u00e4n jotain, joka ei ole radioaktiivinen\nrajapinta IDog {\n  weight: number;\n}\n\n\/\/ M\u00e4\u00e4ritell\u00e4\u00e4n rajapinta s\u00e4ili\u00f6lle, joka voi pit\u00e4\u00e4 sis\u00e4ll\u00e4\u00e4n vain radioaktiivista tavaraa.\ninterface IRadioactiveContainer {\n  add(thing: T): void;\n  getRadioaktiivisuus():number;\n}\n\n\/\/ M\u00e4\u00e4ritell\u00e4\u00e4n luokka, joka toteuttaa radioaktiivisen s\u00e4ili\u00f6n rajapinnan\nclass RadioactiveContainer implements IRadioactiveContainer {\n  private stuff: T[] = [];\n\n  add(asia: T): void {\n    this.stuff.push(thing);\n  }\n\n  getRadioactiveness(): number {\n      return this.stuff.reduce((a, b) =&gt; a + b.ionizingRadiation, 0)\n  }\n}\n\n\/\/ ERROR! Tyyppi 'IDog' ei t\u00e4yt\u00e4 rajoitusta 'IRadioactive'.\n\/\/ Ja on aika brutaalia s\u00e4ilytt\u00e4\u00e4 koiria radioaktiivisen s\u00e4ili\u00f6n sis\u00e4ll\u00e4.\nconst dogsContainer = new RadioactiveContainer();\n\n\/\/ All good fam!\nconst radioactiveContainer = new RadioactiveContainer();\n\n\/\/ Muista lajitella radioaktiiviset j\u00e4tteet - luo erillinen s\u00e4ili\u00f6 vain banaaneille.\nconst bananasContainer = new RadioactiveContainer();<\/code><\/pre>\n\n\n\n<p>Siin\u00e4 kaikki!<\/p>","protected":false},"excerpt":{"rendered":"<p>Geneeriset ohjelmat tarjoavat uudelleenk\u00e4ytett\u00e4vi\u00e4 koodinp\u00e4tki\u00e4, jotka toimivat useiden tyyppien kanssa yhden tyypin sijasta. Generics tarjoaa tavan k\u00e4sitell\u00e4 tyyppi\u00e4 muuttujana ja m\u00e4\u00e4ritell\u00e4 se k\u00e4yt\u00f6n yhteydess\u00e4, kuten funktioparametrit.<\/p>","protected":false},"author":2,"featured_media":3249,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"inline_featured_image":false,"footnotes":""},"categories":[8],"tags":[],"class_list":["post-3248","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-software-development"],"acf":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO Premium plugin v27.3 (Yoast SEO v27.3) - https:\/\/yoast.com\/product\/yoast-seo-premium-wordpress\/ -->\n<title>Generics in TypeScript - The Codest<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/thecodest.co\/fi\/blogi\/geneeriset-tyypit-typescriptissa\/\" \/>\n<meta property=\"og:locale\" content=\"fi_FI\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Generics in TypeScript\" \/>\n<meta property=\"og:description\" content=\"Generics provide reusable bits of code that work with a number of types instead of a single type. 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