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| // Backbone Proxy v0.1.1
//
// https://github.com/biril/backbone-proxy
// Licensed and freely distributed under the MIT License
// Copyright (c) 2014 Alex Lambiris
/*globals exports, define, require, _, Backbone */
// Detect env & export module
// --------------------------
(function (root, createModule) {
'use strict';
// A global `define` method with an `amd` property signifies the presence of an AMD loader
// (e.g. require.js, curl.js)
Iif (typeof define === 'function' && define.amd) {
return define(['underscore', 'backbone', 'exports'], function (_, Backbone, exports) {
return createModule(exports, _, Backbone);
});
}
// A global `exports` object signifies CommonJS-like enviroments that support `module.exports`,
// e.g. Node
Eif (typeof exports === 'object') {
return createModule(exports, require('underscore'), require('backbone'));
}
// Otherwise we assume running in a browser - no AMD loader:
// Save a reference to previous value of `BackboneProxy` before overwriting it - so that it can
// be restored on `noConflict`
var previousBackboneProxy = root.BackboneProxy;
// Create the BackboneProxy module, attaching `BackboneProxy` to global scope
createModule(root.BackboneProxy = {}, _, Backbone);
// And add the `noConflict` method. This sets the `BackboneProxy` _global_ to to its previous
// value (_once_), returning a reference to `BackboneProxy` (_always_)
root.BackboneProxy.noConflict = function () {
var BackboneProxy = root.BackboneProxy;
root.BackboneProxy = previousBackboneProxy;
return (BackboneProxy.noConflict = function () { return BackboneProxy; }).call();
};
// Create module
// -------------
}(this, function (BackboneProxy, _, Backbone) {
'use strict';
var
// Model built-in events. Note that 'all' is not considered to be one of them
builtInEventNames = [
'add', 'remove', 'reset', 'change', 'destroy', 'request', 'sync', 'error', 'invalid'
],
// Names of 'event API' (`Backbone.Event`) methods
eventApiMethodNames = [
'on', 'off', 'trigger', 'once', 'listenTo', 'stopListening', 'listenToOnce'
],
// ### SubscriptionCollection
// A collection of subscriptions, where each is a `<event, callback, context, proxyCallback>`
// 4-tuple. Every `EventEngine` instance maintains a `SubscriptionCollection` instance to
// keep track of registered callbacks and their mapping to _proxy_-callbacks
//
SubscriptionCollection = (function () {
function SubscriptionCollection () {
this._items = [];
}
SubscriptionCollection.prototype = {
_markToKeep: function (propName, propValue) {
if (!propValue) { return; }
for (var i = this._items.length - 1; i >= 0; --i) {
this._items[i].keep = this._items[i][propName] !== propValue;
}
},
// Store subscription of given attributes
store: function (event, callback, context, proxyCallback) {
this._items.push({
event: event,
callback: callback,
context: context,
proxyCallback: proxyCallback
});
},
// Unstore subscriptions that match given `event` / `callback` / `context`. None of the
// params denote mandatory arguments and those given will be used to _filter_ the
// subscriptions to be removed. Invoking the method without any arguments will remove
// _all_ subscriptions. This behaviour is in line with that of `Backbone.Model#off`
unstore: function (event, callback, context) {
var itemsUnstored = [], itemsKept = [];
_(this._items).each(function (item) { item.keep = false; });
this._markToKeep('event', event);
this._markToKeep('callback', callback);
this._markToKeep('context', context);
for (var i = this._items.length - 1; i >= 0; --i) {
(this._items[i].keep ? itemsKept : itemsUnstored).push(this._items[i]);
}
this._items = itemsKept;
return itemsUnstored;
}
};
return SubscriptionCollection;
}()),
// ### Event Engine
// A module that builds on top of `Backbone.Events` to support invoking registered callbacks in
// response to events triggered on a given `proxied`, on behalf of a given `proxy`. Every
// `ModelProxyProto` instance (i.e. every `Proxy.prototype`) contains an Event Engine to
// facilitate forwarding events from proxied to proxy
//
EventEngine = (function () {
function EventEngine(proxy, proxied) {
this._proxy = proxy;
this._proxied = proxied;
this._subscriptions = new SubscriptionCollection();
this._isListeningToProxied = false;
this._markerContext = {};
}
EventEngine.prototype = _({}).extend(Backbone.Events, {
// Get a value indicating whether there's currently _any_ listeners registered on the engine
_hasEvents: function () {
for (var key in this._events) {
Eif (this._events.hasOwnProperty(key)) {
return true;
}
}
return false;
},
// Listen or stop listening for the 'all' event on `proxied` depending on whether there's
// currently _any_ listeners registered on the event engine (equivalently, on the proxy)
_manageSubscriptionToProxied: function () {
var hasEvents = this._hasEvents();
if (this._isListeningToProxied !== hasEvents) {
if (hasEvents) {
this._proxied.on('all', _.bind(function () {
Backbone.Events.trigger.apply(this, arguments);
}, this), this._markerContext);
} else {
this._proxied.off(null, null, this._markerContext);
}
this._isListeningToProxied = hasEvents;
}
},
// For any given subscription (defined by `event` / `callback` / `context`), create a
// _proxy-callback_ - a callback that will be invoked by by Backbone's Event module in
// place of the original caller-provided callback. Depending on the type of the event the
// given subscription refers to, the proxy-callback will take care of appropriately
// setting `model` arguments that may be present (when dealing with model built-in events)
// as well as the context (if it's not explicitly set by the caller)
_createProxyCallback: function (event, callback, context) {
// The context is the one that's already specified _or_ set to the proxy
context || (context = this._proxy);
// If the subscription is for a model built-in event, the proxy-callback will have to
// replace the model argument with the proxy (as Backbone's Event module will set it to
// the proxied when invoking the callback). Same goes for the context
if (_(builtInEventNames).contains(event) || !event.indexOf('change:')) {
return function () {
arguments[0] = this._proxy;
callback.apply(context, arguments);
};
}
// So the subscription doesn't concern a built-in event. If additionally it's not for the
// 'all' event, then we're dealing with a user-defined event. In this case we only have
// to make sure that the callback is invoked the appropriate context
if (event !== 'all') {
return function () {
callback.apply(context, arguments);
};
}
// So The subscription is for the 'all' event: The given callback will run for built-in
// events as well as arbitrary, user-defined events. We'll have to check the type of the
// event at callback-invocation-time and treat it as one of the two cases. (And yes, if
// client-code decides to `trigger()` an event which is named like a built-in but
// doesn't carry the expected parameters, things will go sideways)
return function (event) {
if (_(builtInEventNames).contains(event) || !event.indexOf('change:')) {
arguments[1] = this._proxy;
}
callback.apply(context, arguments);
};
},
on: function (event, callback, context) {
var proxyCallback = this._createProxyCallback(event, callback, context);
this._subscriptions.store(event, callback, context, proxyCallback);
Backbone.Events.on.call(this, event, proxyCallback, context);
this._manageSubscriptionToProxied();
},
off: function (event, callback, context) {
var matchingSubscriptions = this._subscriptions.unstore(event, callback, context);
_(matchingSubscriptions).each(function (subscription) {
Backbone.Events.off.call(this, subscription.event, subscription.proxyCallback, subscription.context);
}, this);
this._manageSubscriptionToProxied();
}
});
return EventEngine;
}()),
// ### Model Proxy Prototype
// The prototype of Proxy, _per given `proxied` model_. Overrides certain `Backbone.Model`
// methods ultimately delegating to the implementations of the given `proxied`
// Create a prototype for Proxy, given a `proxied` model
createModelProxyProtoForProxied = function (proxied) {
function ModelProxyProto() {
var createPersistenceMethod;
// #### Prototype's event API methods - they all delegate to the internal Event Engine
// e.g. `on`, `off`
//
_(eventApiMethodNames).each(function (methodName) {
this[methodName] = function () {
this._eventEngine[methodName].apply(this._eventEngine, arguments);
return this;
};
}, this);
// #### Prototype's methods that should always be invoked with `this` set to `proxied`
// e.g. `set`
// This ensures that
//
// * all other model methods in the call-graph of the invoked method (e.g. `proxied.set`)
// are also invoked with `this` set to `proxied`.
// * all properties which may be set on the model as part of the invoked method's code
// path are set on `proxied`
//
// For example, this ensures that the `model` parameter made available to event listeners
// attached to `proxied` will be `proxied` - not `proxy` (which would otherwise be the
// case). In terms of set properties, consider `validationError` which also needs to be
// set on `proxied` - not `proxy`.
// Generally, we just need to forward to `proxied`
_(['isNew', 'url']).each(function (methodName) {
this[methodName] = function () {
return proxied[methodName]();
};
}, this);
// Specifically, for the case of `set`, we need to replace the returned reference with
// `this`. To get proper chaining
this.set = function () {
return proxied.set.apply(proxied, arguments) ? this : false;
};
// #### Prototype's persistence methods
// i.e. `fetch`, `save` & `destroy`
// Create persistence method of `methodName`, where `isWithAttributes` indicates whether
// the method excepts attributes (`save`) or just options (`fetch`, `destroy`)
createPersistenceMethod = function (methodName, isWithAttributes) {
return function () {
var opts, success, error, args;
opts = arguments[isWithAttributes ? 1 : 0];
opts = opts ? _.clone(opts) : {};
success = opts.success;
error = opts.error;
success && (opts.success = _.bind(function (model, response, opts) {
success(this, response, opts);
}, this));
error && (opts.error = _.bind(function (model, response, opts) {
error(this, response, opts);
}, this));
args = isWithAttributes ? [arguments[0], opts] : [opts];
return proxied[methodName].apply(proxied, args);
};
};
this.fetch = createPersistenceMethod('fetch', false);
this.destroy = createPersistenceMethod('destroy', false);
this.save = createPersistenceMethod('save', true);
this._proxied = proxied;
}
ModelProxyProto.prototype = proxied;
return ModelProxyProto;
};
// ### BackboneProxy
// The BackboneProxy module. Features a single `extend` method by means of which a proxy 'class'
// `Proxy` may be created. E.g `UserProxy = BackboneProxy.extend(user)`. Proxy classes may be
// instantiated into proxies, e.g. `user = new UserProxy()`
// Return the BackboneProxy module
return _(BackboneProxy).extend({
extend: function (proxied) {
var ctor, ModelProxyProto;
ctor = function ModelProxy() {
this._eventEngine = new EventEngine(this, proxied);
};
ModelProxyProto = createModelProxyProtoForProxied(proxied);
ctor.prototype = new ModelProxyProto();
return ctor;
}
});
}));
|