{"id":1624,"date":"2022-01-28T18:07:17","date_gmt":"2022-01-28T17:07:17","guid":{"rendered":"https:\/\/nguenkam.com\/blog\/?p=1624"},"modified":"2022-01-28T18:22:37","modified_gmt":"2022-01-28T17:22:37","slug":"typescript-multiple-inheritance-issue","status":"publish","type":"post","link":"https:\/\/nguenkam.com\/blog\/index.php\/2022\/01\/28\/typescript-multiple-inheritance-issue\/","title":{"rendered":"TypeScript & Inheritance"},"content":{"rendered":"\n

Inheritance <\/span>is an aspect of OOPs languages, which provides the ability of a program to create a new class from an existing class. It is a mechanism which acquires the\u00a0properties<\/strong>\u00a0and\u00a0behaviors<\/strong>\u00a0of a class from another class. The class whose members are inherited is called the\u00a0base class<\/strong>, and the class that inherits those members is called the\u00a0derived\/child\/subclass<\/strong>. In child class, we can override or modify the behaviors of its parent class.<\/p>\n\n\n\n

Before ES6 (ES2015) , JavaScript uses\u00a0functions<\/strong>\u00a0and\u00a0prototype-based<\/strong>\u00a0inheritance, but TypeScript supports the\u00a0class-based<\/strong>\u00a0inheritance which comes from ES6 version. The TypeScript uses class inheritance through the\u00a0extends<\/strong>\u00a0keyword.\u00a0<\/p>\n\n\n\n

PS:<\/span>TypeScript does not support multiple inheritance<\/strong>.<\/em><\/p>\n\n\n\n

\u00a0TypeScript supports only\u00a0single<\/strong>\u00a0inheritance and\u00a0multilevel<\/strong>\u00a0inheritance.<\/p>\n\n\n\n

<\/p>\n\n\n\n

Types of Inheritance<\/h4>\n\n\n\n

We can classify the inheritance into the five types. These are:<\/p>\n\n\n\n

  • Single Inheritance<\/li>
  • Multilevel Inheritance<\/li>
  • Multiple Inheritance<\/li>
  • Hierarchical Inheritance<\/li>
  • Hybrid Inheritance<\/li><\/ul>\n\n\n\n
    \"\"<\/figure>\n\n\n\n
    <\/div>\n\n\n\n

    How can we do, if we face a “multiple inheritance”<\/em> issue in typescript ? <\/h4>\n\n\n\n

    Workaround 1 :<\/span><\/h4>\n\n\n\n

    first tip: whenever we come across a multiple inheritance problem, let\u00b4s think “multiple level inheritance over multiple inheritance”<\/em><\/strong> to see if that’ll do the job:<\/p>\n\n\n\n

    Class B extends A, Class C extendes B, <\/em>and so on ..<\/em>. <\/span><\/p>\n\n\n\n

    Workaround 2<\/span><\/h4>\n\n\n\n

    There is a feature in TypeScript that allows you to use Mixins<\/strong><\/em> to create re-usable small objects. You can compose these into larger objects using multiple inheritance (multiple inheritance is not allowed for classes, but it is allowed for mixins<\/strong><\/em> – which are like interfaces with an associated implenentation).<\/p>\n\n\n\n

    Here is a quick Mixins demo… first, the flavours that you want to mix:<\/p>\n\n\n\n

    class CanEat {\r\n    public eat() {\r\n        alert('Munch Munch.');\r\n    }\r\n}\r\n\r\nclass CanSleep {\r\n    sleep() {\r\n        alert('Zzzzzzz.');\r\n    }\r\n}<\/code><\/pre>\n\n\n\n
    Then the magic method for Mixin creation (you only need this once somewhere in your program…)<\/p>\n\n\n\n
    function applyMixins(derivedCtor: any, baseCtors: any[]) {\r\n    baseCtors.forEach(baseCtor => {\r\n        Object.getOwnPropertyNames(baseCtor.prototype).forEach(name => {\r\n             if (name !== 'constructor') {\r\n                derivedCtor.prototype[name] = baseCtor.prototype[name];\r\n            }\r\n        });\r\n    }); \r\n}<\/code><\/pre>\n\n\n\n
    And then you can create classes with multiple inheritance from mixin flavours:<\/p>\n\n\n\n
    class Being implements CanEat, CanSleep {\r\n        eat: () => void;\r\n        sleep: () => void;\r\n}\r\napplyMixins (Being, [CanEat, CanSleep]);<\/code><\/pre>\n\n\n\n
    Note that there is no actual implementation in this class – just enough to make it pass the requirements of the “interfaces”. But when we use this class – it all works.<\/p>\n\n\n\n
    var being = new Being();\r\n\r\n\/\/ Zzzzzzz...\r\nbeing.sleep();<\/code><\/pre>\n\n\n\n
    <\/div>\n","protected":false},"excerpt":{"rendered":"
    Inheritance is an aspect of OOPs languages, which provides the ability of a program to create a new class from an existing class. It is a mechanism which acquires the\u00a0properties\u00a0and\u00a0behaviors\u00a0of a class from another class. The class whose members are inherited is called the\u00a0base class, and the class that inherits those members is called the\u00a0derived\/child\/subclass. […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[83],"tags":[393,473,474,471,472],"_links":{"self":[{"href":"https:\/\/nguenkam.com\/blog\/index.php\/wp-json\/wp\/v2\/posts\/1624"}],"collection":[{"href":"https:\/\/nguenkam.com\/blog\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/nguenkam.com\/blog\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/nguenkam.com\/blog\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/nguenkam.com\/blog\/index.php\/wp-json\/wp\/v2\/comments?post=1624"}],"version-history":[{"count":3,"href":"https:\/\/nguenkam.com\/blog\/index.php\/wp-json\/wp\/v2\/posts\/1624\/revisions"}],"predecessor-version":[{"id":1628,"href":"https:\/\/nguenkam.com\/blog\/index.php\/wp-json\/wp\/v2\/posts\/1624\/revisions\/1628"}],"wp:attachment":[{"href":"https:\/\/nguenkam.com\/blog\/index.php\/wp-json\/wp\/v2\/media?parent=1624"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/nguenkam.com\/blog\/index.php\/wp-json\/wp\/v2\/categories?post=1624"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/nguenkam.com\/blog\/index.php\/wp-json\/wp\/v2\/tags?post=1624"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}