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// Copyright 2012 The Closure Library Authors. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS-IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
/**
* @fileoverview An implementation of {@code Observable} that can be
* used as base class or composed into another class that wants to
* implement {@code Observable}.
*/
goog.provide('goog.labs.observe.SimpleObservable');
goog.require('goog.Disposable');
goog.require('goog.array');
goog.require('goog.asserts');
goog.require('goog.labs.observe.Notice');
goog.require('goog.labs.observe.Observable');
goog.require('goog.labs.observe.Observer');
goog.require('goog.object');
/**
* A simple implementation of {@code goog.labs.observe.Observable} that can
* be used as a standalone observable or as a base class for other
* observable object.
*
* When another class wants to implement observable without extending
* {@code SimpleObservable}, they can create an instance of
* {@code SimpleObservable}, specifying {@code opt_actualObservable},
* and delegate to the instance. Here is a trivial example:
*
* <pre>
* ClassA = function() {
* goog.base(this);
* this.observable_ = new SimpleObservable(this);
* this.registerDisposable(this.observable_);
* };
* goog.inherits(ClassA, goog.Disposable);
*
* ClassA.prototype.observe = function(observer) {
* this.observable_.observe(observer);
* };
*
* ClassA.prototype.unobserve = function(observer) {
* this.observable_.unobserve(observer);
* };
*
* ClassA.prototype.notify = function(opt_data) {
* this.observable_.notify(opt_data);
* };
* </pre>
*
* @param {!goog.labs.observe.Observable=} opt_actualObservable
* Optional observable object. Defaults to 'this'. When used as
* base class, the parameter need not be given. It is only useful
* when using this class to implement implement {@code Observable}
* interface on another object, see example above.
* @constructor
* @implements {goog.labs.observe.Observable}
* @extends {goog.Disposable}
*/
goog.labs.observe.SimpleObservable = function(opt_actualObservable) {
goog.base(this);
/**
* @type {!goog.labs.observe.Observable}
* @private
*/
this.actualObservable_ = opt_actualObservable || this;
/**
* Observers registered on this object.
* @type {!Array.<!goog.labs.observe.Observer>}
* @private
*/
this.observers_ = [];
};
goog.inherits(goog.labs.observe.SimpleObservable, goog.Disposable);
/** @override */
goog.labs.observe.SimpleObservable.prototype.observe = function(observer) {
goog.asserts.assert(!this.isDisposed());
// Registers the (type, observer) only if it has not been previously
// registered.
var shouldRegisterObserver = !goog.array.some(this.observers_, goog.partial(
goog.labs.observe.Observer.equals, observer));
if (shouldRegisterObserver) {
this.observers_.push(observer);
}
return shouldRegisterObserver;
};
/** @override */
goog.labs.observe.SimpleObservable.prototype.unobserve = function(observer) {
goog.asserts.assert(!this.isDisposed());
return goog.array.removeIf(this.observers_, goog.partial(
goog.labs.observe.Observer.equals, observer));
};
/** @override */
goog.labs.observe.SimpleObservable.prototype.notify = function(opt_data) {
goog.asserts.assert(!this.isDisposed());
var notice = new goog.labs.observe.Notice(this.actualObservable_, opt_data);
goog.array.forEach(
goog.array.clone(this.observers_), function(observer) {
observer.notify(notice);
});
};
/** @override */
goog.labs.observe.SimpleObservable.prototype.disposeInternal = function() {
this.observers_.length = 0;
};
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