olical / heir

Helper functions for prototypical inheritance in JavaScript

Heir

Helper functions for prototypical inheritance in JavaScript.

Use the source code and JSDoc comments as documentation, here's a quick example to get you started.

const heir = require('heir')

// Create the base class.
function Base() {}

// Add a method.
Base.prototype.foo = function () {
  return 'Base#foo'
}

// Create a sub class which inherits from base.
function Sub() {}
heir.inherit(Sub, Base)

// Mix in some functionality enhancing objects.
heir.mixin(Sub, events)
heir.mixin(Sub, pooling)

// Change the original method.
Sub.prototype.foo = function () {
  return [
    'Sub#foo',
    Sub._super.foo.call(this)
  ].join(', ')
}

// Create an instance of Sub and call it's method.
const s = new Sub()
s.foo() // Returns "Sub#foo, Base#foo"

Unlicense

This project is given to you under the unlicense, as documented in the UNLICENSE file in this directory. Enjoy.

heir's Issues

Doesn't exist in npm

Heir doesn't exist in npm

Should I rewrite a lot of this, but better?

I built this almost a year ago, I've learnt a lot in that time. One of the main things related to this project is my knowledge about prototypical inheritance and how I think it should be done.

I've summed up how I think it should now be approached within this post: http://oli.me.uk/2013/06/01/prototypical-inheritance-done-right/

I would quite like to restructure a lot of this code so it still kept the old mixin style but also had a new method that actually extends the class. At the moment, if you extend something, it won't actually be an instance of the parent class.

var Parent = function(){}
var Child = function(){}.extend(Parent);

var a = new Parent();
var b = new Child();

a instanceof Child; // false, which is correct
a instanceof Parent; // true, also correct

b instanceof Child; // true, this is fine
b instanceof Parent; // false, but it should be true

If I added in my new extension method for extending and then kept the old code as a kind of mixin for multiple inheritance, I think this project would become a lot more useful.

At the moment it is not implemented how it should be. It's only like this because I did not know what I know now all those months ago when I wrote it.

I would like to restructure a lot of this but keep the same essence. It will do the same thing, but in a slightly different way. I'd ideally like to do this before firing it off into the world of package managers too.

I'd also like to remove the modification of Function.prototype, but I'm not sure about that one. It feels wrong.

Thoughts?

Bug/Error with the _super property in latest version

I found a bug when using the _super property inside a subclass. Please check the fiddle provided below
I used the same code as in your demo.

"Uncaught TypeError: Cannot read property 'foo' of undefined
at Sub.foo ((index)..."

I believe this error is due to this line :

destination._super = source.prototype

If changed to

destination.prototype._super = source.prototype

then it will work.

Version

v3.0.0

Test Case

https://jsfiddle.net/josefano09/w81xdg45/1/

Steps to reproduce

Use heir.inherit(Sub, Base); and then inside the Sub class try to call this._super. The above error will show in the console.