mixinable

Mixinable

 

mixinable is a small functional utility library allowing you to use mixins in your code. More specifically, it allows you to create mixin containers that apply mixin method application strategies to mixin method implementations.

Mixins are plain Objects (or hashes) that can easily be shared, modified and extended using standard language features such as spread syntax or Object.assign().

mixinable allows you to provide custom constructor functions and supports asynchronous methods returning Promises. It is built in a functional way, allowing you to, for example, apply fn.bind().

Installation

Using NPM:

npm install -S mixinable

Using Yarn:

yarn add mixinable

To be able to use mixinable, you will have to make sure your environment supports Promise and Object.assign()/Object.keys(): if you need to support IE11, you will have to polyfill those features.

API

define(definition)

The main export of mixinable is a define() function accepting a mixin container definition. This definition hash is made up of strategy functions prescribing how to handle different mixin methods you provide.

It returns a variadic mixin() function that accepts the mixin definitions you want to apply and returns a create() function. Mixin definitions are hashes containing mixin method implementations that are being applied using the aforementioned strategies.

And that create() function accepts whatever arguments your constructor()s accept.

Example

import define from 'mixinable';

const mixin = define({
  // mixin strategy function
  bar (functions, arg) {
    return functions.pop()(arg);
  }
});

const create = mixin({
  // mixin implementation
  bar (arg) {
    console.log(arg);
  }
});

const foo = create();

foo.bar('yeah!');
// yeah!

Speaking of which: mixinable creates a separate hidden mixin instance for every mixin you provide. When used inside a mixin method, this refers to this hidden instance.

Mixin methods not included in your definition are only accessible from within the mixin instance itself, but not from the outside.

Example

import define from 'mixinable';

const mixin = define({
  bar (functions, arg) {
    return functions.pop()(arg);
  }
});

const create = mixin({
  // mixin method implementations
  bar (arg) {
    this.qux(arg);
  },
  // private mixin method
  qux (arg) {
    console.log(arg);
  }
});

const foo = create();

foo.bar('yeah!');
// yeah!

console.log(typeof foo.bar, typeof foo.qux);
// function undefined

Mixin definitions can be (or contain) custom constructors. These functions are being passed the create() function's arguments upon creation.

Example

import define from 'mixinable';

const mixin = define();

const create = mixin(
  // mixin contructors
  {
    constructor: function (arg) {
      console.log(arg);
    }
  },
  class {
    constructor (arg) {
      console.log(arg);
    }
  }
);

create('yee-hah!');
// yee-hah!
// yee-hah!

define.override

override is a helper implementating a mixin strategy that resembles classical inherintance (class ... extends): it simply calls the last method implementation.

Example

import define, { override } from 'mixinable';

const mixin = define({
  // mixin strategy function
  bar: override
});

const create = mixin(
  // mixin method implementations
  {
    bar () {
      console.log(1);
    }
  },
  class {
    bar () {
      console.log(2);
    }
  }
);

const foo = create();

foo.bar();
// 2

override returns a Promise if one of its implementations does. If you want it to always return a Promise, i.e. if you can not be sure whether one of your implementations might return one, please use define.async.override.

define.parallel

parallel is a helper implementating a mixin strategy that executes all defined implementations in parallel. This is probably most useful if asynchronous implementations are involved.

Example

import define, { parallel } from 'mixinable';

const mixin = define({
  // mixin strategy function
  bar: parallel
});

const create = mixin(
  // mixin method implementations
  {
    bar (val, inc) {
      return Promise.resolve(val + inc);
    }
  },
  class {
    bar (val, inc) {
      return val + inc;
    }
  }
);

const foo = create();

foo.bar(0, 1).then(res => console.log(res));
// [1, 1]

parallel returns a Promise if one of its implementations does. If you want it to always return a Promise, i.e. if you can not be sure whether one of your implementations might return one, please use define.async.parallel.

define.pipe

pipe is a helper implementating a strategy that passes each implementation's output to the next, using the first argument as the initial value. All other arguments are being passed to all implementations as-is.

Example

import define, { pipe } from 'mixinable';

const mixin = define({
  // mixin strategy function
  bar: pipe
});

const create = mixin(
  // mixin method implementations
  {
    bar (val, inc) {
      return Promise.resolve(val + inc);
    }
  },
  class {
    bar (val, inc) {
      return (val + inc);
    }
  }
);

const foo = create();

foo.bar(0, 1).then(res => console.log(res));
// 2

pipe returns a Promise if one of its implementations does. If you want it to always return a Promise, i.e. if you can not be sure whether one of your implementations might return one, please use define.async.pipe.

define.compose

compose works essentially identically as pipe, but in reverse order: the very last implementation receives the initial value and the first implementation returns the final output.

Example

import define, { compose } from 'mixinable';

const mixin = define({
  // mixin strategy function
  bar: compose
});

// ...

compose returns a Promise if one of its implementations does. If you want it to always return a Promise, i.e. if you can not be sure whether one of your implementations might return one, please use define.async.compose.

Custom Strategies

You can supply your own mixin strategies: such strategies are plain functions that receive the defined implementations as their first argument. The following example shows a naïve re-implementation of the override strategy.

Example

import define from 'mixinable';

const mixin = define({
  // mixin strategy function
  bar (functions, ...args) {
    functions.pop().apply(null, args);
  }
});

const create = mixin({
  // mixin method implementation
  bar (arg) {
    console.log(arg);
  }
});

const foo = create();

foo.bar(1);
// 1

Utilities

define.async

All of the strategies described above return a Promise if one of their implementations does. If you want them to always return a Promise please use define.async.{override,parallel,pipe,compose}.

define.isMixinable(object)

If you need to check whether an object actually is an instance of a mixinable, you can simply test it using this function that returns true or false.

Contributing

If you want to contribute to this project, create a fork of its repository using the GitHub UI. Check out your new fork to your computer:

mkdir mixinable && cd $_
git clone [e-mail]:user/mixinable.git

Afterwards, you can yarn install the required dev dependencies and start hacking away. When you are finished, please do go ahead and create a pull request.

mixinable itself is almost entirely written in ECMAScript 5 and adheres to semistandard code style. Please make sure your contribution does, too.

Changelog

1.4.0 (2018-03-06)

Features

• add sync helper export (c7ab765)

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