Rails-like `delegate` in Coffeescript

rails_delegate.coffee

# Micro-optimized, with extra-function (so it's not redefined at each call)

delegate = (delegatorConstructor, delegeeProp, method) ->
  delegatorConstructor.prototype[ method ] = ->
    this[ delegeeProp ][ method ].apply( this[ delegeeProp ], arguments )

Function.prototype.delegate = ( methodNames..., toProp ) ->
  delegeeProp = toProp.to
  for method in methodNames
    delegate(this, delegeeProp, method)

rails_delegate_alt.coffee

# Without `that`, one method

Function.prototype.delegate = ( methodNames..., toProp ) ->
  delegeeProp = toProp.to
  for method in methodNames
    do (constr = this, delegeeProp, method) ->
      constr.prototype[ method ] = ->
        console.log this
        this[ delegeeProp ][ method ].apply( this[ delegeeProp ], arguments )

rails_delegate_alt.js

// Ready to use JS version, generated from the Coffeescript (= ugly...)

var __slice = [].slice;
Function.prototype.delegate = function() {
  var delegeeProp, method, methodNames, toProp, _i, _j, _len, _results;
  methodNames = 2 <= arguments.length ? __slice.call(arguments, 0, _i = arguments.length - 1) : (_i = 0, []), toProp = arguments[_i++];
  delegeeProp = toProp.to;
  _results = [];
  for (_j = 0, _len = methodNames.length; _j < _len; _j++) {
    method = methodNames[_j];
    _results.push((function(constr, delegeeProp, method) {
      return constr.prototype[method] = function() {
        console.log(this);
        return this[delegeeProp][method].apply(this[delegeeProp], arguments);
      };
    })(this, delegeeProp, method));
  }
  return _results;
};

rails_delegate_that.coffee

# With `that`, one method

Function.prototype.delegate = ( methodNames..., toProp ) ->
  delegeeProp = toProp.to
  that = this
  for method in methodNames
    do (method) ->
      that.prototype[ method ] = ->
        this[ delegeeProp ][ method ].apply( this[ delegeeProp ], arguments )