tsmixin

Simple mixin for TypeScript

install

npm i tsmixin

motivation

TypeScript Handbook entry on mixins describes an approach thal allows for mixins, but is a bit tedious to code: forces you to add class interface override, apply the mixins separately, and requires to add a helper function to your code base.

If you, like me, wanted it as simple as class X extends mixin(X, Y, Z) { ... then this package might be of use.

Under the hood

The mixin() or extmixin() functions create and return anonymous class, with the mixin properties added.

Example #1: mixin()

E.g. mixin with no constructor/super call

import { mixin } from 'tsmixin';

class Callable {
  constructor(public a: number) {}

  call() {
    console.log("Call!")
  }
}

// Mixin class #2
abstract class Activable {
  active: boolean;
  activate() {
    this.active = true;
    console.log("Activating…");
  }
  deactive() {
    this.active = false;
    console.log("Deactivating…");
  }
}

class MyClass extends mixin(Callable, Activable) { }

const my = new MyClass();
my.call();
my.activate();

Example #2: extmixin()

E.g. extend the first argument class and mix in the rest

import { extmixin } from 'tsmixin';

class Callable {
  constructor(public aNumber: number) {}

  call() {
    console.log("Call!")
  }
}

// Mixin class #2
abstract class Activable {
  active: boolean;
  activate() {
    this.active = true;
    console.log("Activating…");
  }
  deactive() {
    this.active = false;
    console.log("Deactivating…");
  }
}


class MyClass extends extmixin(Callable, Activable) { }

const my = new MyClass(1); // notice that it will require the constructor arguments of Callable
my.call();
my.activate();
console.log(my.aNumber); // 1

Notes

• extmixin() can not use an abstract class as the extnded class, because of this intentional TypeScript limitation