marionette.view.mixin.js

// Using lodash so we can use isPlainObject
var
  _ = require('lodash'),
  Marionette = require('backbone.marionette');

var _constructor = Marionette.View.prototype.constructor;

Marionette.View = Marionette.View.extend({
  constructor: function (attributes, options) {
    var self = this;
    // If mixins is a function, pass in the attributes [model, etc]
    // If mixins is an object just use that
    var mixins = this.mixins ? _.isFunction(this.mixins) ? this.mixins(attributes) : this.mixins : null;
    var collisions = {};

    _.each(mixins, function(mixin) {
      _.each(mixin, function(value, key) {
        if (_.isPlainObject(value)) {
          self[key] = _.extend({}, self[key] || {}, value);
        } else if (_.isFunction(value)) {
          if (self[key]) {
            collisions[key] = collisions[key] || [self[key]];
            collisions[key].push(value);
          }
          self[key] = value;
        } else if ( ! self[key] ) {
          self[key] = value;
        } else if ( value === null) { // This allows completely overwriting a value instead of dealing with a collision
          self[key] = null;
        }
      });
    });

    _.each(collisions, function(propertyValues, propertyName) {
      self[propertyName] = function() {
        var args = [].slice.call(arguments);
        var returnValue;

        _.each(propertyValues, _.bind(function(value) {
          returnValue = ( _.isFunction(value) ? value.apply(this, args) : value ) || returnValue;
          args.push(returnValue);
        }, this));

        return returnValue;
      };
    });

    _constructor.call(this, attributes, options);
  }
});