99 lines
2.9 KiB
JavaScript
99 lines
2.9 KiB
JavaScript
var async = require('async');
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var utils = require('./utils');
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module.exports = ObserverMixin;
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/**
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* ObserverMixin class. Use to add observe/notifyObserversOf APIs to other
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* classes.
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*
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* @class ObserverMixin
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*/
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function ObserverMixin() {
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}
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/**
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* Register an asynchronous observer for the given operation (event).
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* @param {String} operation The operation name.
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* @callback {function} listener The listener function. It will be invoked with
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* `this` set to the model constructor, e.g. `User`.
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* @param {Object} context Operation-specific context.
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* @param {function(Error=)} next The callback to call when the observer
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* has finished.
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* @end
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*/
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ObserverMixin.observe = function(operation, listener) {
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this._observers = this._observers || {};
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if (!this._observers[operation]) {
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this._observers[operation] = [];
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}
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this._observers[operation].push(listener);
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};
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/**
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* Unregister an asynchronous observer for the given operation (event).
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* @param {String} operation The operation name.
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* @callback {function} listener The listener function.
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* @end
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*/
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ObserverMixin.removeObserver = function(operation, listener) {
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if (!(this._observers && this._observers[operation])) return;
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var index = this._observers[operation].indexOf(listener);
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if (index !== -1) {
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return this._observers[operation].splice(index, 1);
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}
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};
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/**
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* Unregister all asynchronous observers for the given operation (event).
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* @param {String} operation The operation name.
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* @end
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*/
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ObserverMixin.clearObservers = function(operation) {
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if (!(this._observers && this._observers[operation])) return;
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this._observers[operation].length = 0;
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};
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/**
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* Invoke all async observers for the given operation.
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* @param {String} operation The operation name.
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* @param {Object} context Operation-specific context.
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* @param {function(Error=)} callback The callback to call when all observers
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* has finished.
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*/
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ObserverMixin.notifyObserversOf = function(operation, context, callback) {
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var observers = this._observers && this._observers[operation];
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if (!callback) callback = utils.createPromiseCallback();
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this._notifyBaseObservers(operation, context, function doNotify(err) {
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if (err) return callback(err, context);
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if (!observers || !observers.length) return callback(null, context);
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async.eachSeries(
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observers,
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function notifySingleObserver(fn, next) {
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var retval = fn(context, next);
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if (retval && typeof retval.then === 'function') {
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retval.then(
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function() { next(); },
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next // error handler
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);
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}
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},
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function(err) { callback(err, context) }
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);
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});
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return callback.promise;
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}
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ObserverMixin._notifyBaseObservers = function(operation, context, callback) {
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if (this.base && this.base.notifyObserversOf)
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this.base.notifyObserversOf(operation, context, callback);
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else
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callback();
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}
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