L.Class does not initialize when extended with Coffeescript Class

[238855]

Expected class Layer extends L.Class to work the same as
Layer = L.Class.extend({}) but the former was not initializing correctly

[calvinmetcalf]

So your problem here is that Leaflet and CoffeeScript both add classes to JavaScript in incompatible ways.

Short answer: class and extend while they look the same in Leaflet and CofeeScript should be treated as totally seperate things.

Long answer:

class Layer extends L.Class

in JavaScript is

var Layer,
  __hasProp = {}.hasOwnProperty,
  __extends = function(child, parent) { for (var key in parent) { if (__hasProp.call(parent, key)) child[key] = parent[key]; } function ctor() { this.constructor = child; } ctor.prototype = parent.prototype; child.prototype = new ctor(); child.__super__ = parent.prototype; return child; };

Layer = (function(_super) {

  __extends(Layer, _super);

  function Layer() {
    return Layer.__super__.constructor.apply(this, arguments);
  }

  return Layer;

})(L.Class);

but in leaflet

Layer = L.Class.extend({})

is really

L.Class.extend = function (props) {

    // extended class with the new prototype
    var NewClass = function () {

        // call the constructor
        if (this.initialize) {
            this.initialize.apply(this, arguments);
        }

        // call all constructor hooks
        if (this._initHooks) {
            this.callInitHooks();
        }
    };

    // instantiate class without calling constructor
    var F = function () {};
    F.prototype = this.prototype;

    var proto = new F();
    proto.constructor = NewClass;

    NewClass.prototype = proto;

    //inherit parent's statics
    for (var i in this) {
        if (this.hasOwnProperty(i) && i !== 'prototype') {
            NewClass[i] = this[i];
        }
    }

    // mix static properties into the class
    if (props.statics) {
        L.extend(NewClass, props.statics);
        delete props.statics;
    }

    // mix includes into the prototype
    if (props.includes) {
        L.Util.extend.apply(null, [proto].concat(props.includes));
        delete props.includes;
    }

    // merge options
    if (props.options && proto.options) {
        props.options = L.extend({}, proto.options, props.options);
    }

    // mix given properties into the prototype
    L.extend(proto, props);

    proto._initHooks = [];

    var parent = this;
    // add method for calling all hooks
    proto.callInitHooks = function () {

        if (this._initHooksCalled) { return; }

        if (parent.prototype.callInitHooks) {
            parent.prototype.callInitHooks.call(this);
        }

        this._initHooksCalled = true;

        for (var i = 0, len = proto._initHooks.length; i < len; i++) {
            proto._initHooks[i].call(this);
        }
    };

    return NewClass;
};
Layer = L.Class.extend({})

[238855]

Yea I understand the difference, and it's obviously not a major issue. Backbone addressed this in v0.3.0 and I recently came across a similar issue raised here: PaulUithol/Backbone-relational#91.

It's an issue that many CoffeeScript users will encounter so just wanted to make you aware

[calvinmetcalf]

it looks like backbone addressed this by adding

child.__super__ = parent.prototype;

to _.extend

I wonder if adding

NewClass.__super__ = parent.prototype;

to L.Class.extend would solve it in leaflet.

[calvinmetcalf]

so tried that on my private branch, you can checkout the demo here, by adding that line you can do

Common = L.TileLayer.extend 
  initialize: (options) ->
    L.TileLayer::initialize.call this, @url, options
MapQuestOpen = L.TileLayer.Common.extend
  url: "http://otile{s}.mqcdn.com/tiles/1.0.0/osm/{z}/{x}/{y}.jpeg"
  options:
    subdomains: "1234"
mq = new MapQuestOpen

we can in do

class Common extends L.TileLayer
  initialize:(options)->
    super @url, options

class MapQuestOpen extends Common
  url: 'http://otile{s}.mqcdn.com/tiles/1.0.0/osm/{z}/{x}/{y}.jpeg',
  initialize:->
    super {attribution:mapQuestAttr + osmDataAttr, subdomains:'1234'}
mq = new MapQuestOpen

I rarely use extends in CoffeeScript (I do use coffeescript) so I'm not sure how well this works compared to say backbone initialize seems wonky especially.

[238855]

Looks good @calvinmetcalf - thanks for showing me the solution
Will you submit this to the master branch?

[mourner]

Merged!