ts-mixin-extended
Extended mixin function for TypeScript.
Offers support for chaining mixins extending a common base class or exposing methods not depending on one.
Since TypeScript 2.2 Mix-in classes are supported, but still somewhat unwieldy. This packages aims to simplify chainning mixins while still offering all the Typings support and most of the flexibility of native ts:
// Default approach
class Dog extends Domesticated(Barking(PackHunting(Carnivore(FourLegged(Animal))))) {}
// Using the extended mixin function
class Dog extends mixin(Animal, FourLegged, Carnivore, PackHunting, Barking, Domesticated) {}Features
- comprehensible chaining of mixins
- strong typechecking for mixins with a common base class
Usage
The package exposes one, and only one, function: mixin.
It accepts one base class and, all of them standalone or extending the base class:
import mixin, { MixinConstructor } from '../src';
class Positionable {
public constructor(public x = 0, public y = 0) {}
public setPosition(x: number, y: number) { this.x = x; this.y = y; }
}
function Walkable<TBase extends MixinConstructor<Positionable>>(Base: TBase) {
return class Walkable extends Base {
public forward() { this.x++; }
public backward() { this.x--; }
};
}
function Jumpable<TBase extends MixinConstructor<Positionable>>(Base: TBase) {
return class Jumpable extends Base {
public jump() { this.y++; }
};
}
// Person now has the attributes `x` and `y` and the methods:
// `setPosition`, `forward`, `backward` and `jump`
class Person extends mixin(Positionable, Walkable, Jumpable) {}For mixins not extending a common base class, an empty anonymous class can be given:
export function Loggable(Base: MixinConstructor) {
return class Loggable extends Base {
public log(message: string) { throw new Error(404); }
};
}
export function Screamable(Base: MixinConstructor) {
return class Screamable extends Base {
public scream(message: string) { console.log(message.slice(0, 140).toUpperCase()); }
};
}
class TheInternet extends mixin(class {}, Loggable, Screamable) {}