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[Code Style] Use prototypes in persistence bundles
WTD-1482
This commit is contained in:
Victor Woeltjen
@ -38,71 +38,17 @@ define(
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*
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* @memberof platform/persistence/cache
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* @constructor
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* @param {string[]} CACHE_SPACES persistence space names which
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* @param {string[]} cacheSpaces persistence space names which
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* should be cached
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* @param {PersistenceService} persistenceService the service which
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* implements object persistence, whose inputs/outputs
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* should be cached.
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* @implements {PersistenceService}
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*/
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function CachingPersistenceDecorator(CACHE_SPACES, persistenceService) {
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var spaces = CACHE_SPACES || [], // List of spaces to cache
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function CachingPersistenceDecorator(cacheSpaces, persistenceService) {
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var spaces = cacheSpaces || [], // List of spaces to cache
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cache = {}; // Where objects will be stored
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// Update the cached instance of an object to a new value
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function replaceValue(valueHolder, newValue) {
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var v = valueHolder.value;
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// If it's a JS object, we want to replace contents, so that
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// everybody gets the same instance.
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if (typeof v === 'object' && v !== null) {
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// Only update contents if these are different instances
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if (v !== newValue) {
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// Clear prior contents
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Object.keys(v).forEach(function (k) {
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delete v[k];
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});
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// Shallow-copy contents
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Object.keys(newValue).forEach(function (k) {
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v[k] = newValue[k];
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});
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}
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} else {
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// Otherwise, just store the new value
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valueHolder.value = newValue;
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}
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}
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// Place value in the cache for space, if there is one.
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function addToCache(space, key, value) {
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if (cache[space]) {
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if (cache[space][key]) {
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replaceValue(cache[space][key], value);
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} else {
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cache[space][key] = { value: value };
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}
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}
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}
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// Create a function for putting value into a cache;
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// useful for then-chaining.
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function putCache(space, key) {
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return function (value) {
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addToCache(space, key, value);
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return value;
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};
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}
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// Wrap as a thenable; used instead of $q.when because that
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// will resolve on a future tick, which can cause latency
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// issues (which this decorator is intended to address.)
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function fastPromise(value) {
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return {
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then: function (callback) {
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return fastPromise(callback(value));
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}
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};
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}
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// Arrayify list of spaces to cache, if necessary.
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spaces = Array.isArray(spaces) ? spaces : [ spaces ];
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@ -111,103 +57,107 @@ define(
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cache[space] = {};
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});
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// Provide PersistenceService interface; mostly delegate to the
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// decorated service, intervene and cache where appropriate.
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this.spaces = spaces;
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this.cache = cache;
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this.persistenceService = persistenceService;
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}
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// Wrap as a thenable; used instead of $q.when because that
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// will resolve on a future tick, which can cause latency
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// issues (which this decorator is intended to address.)
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function fastPromise(value) {
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return {
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/**
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* List all persistence spaces that are supported by the
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* decorated service.
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* @memberof CachingPersistenceDecorator#
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* @returns {Promise.<string[]>} spaces supported
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* @memberof platform/persistence/cache.CachingPersistenceDecorator#
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*/
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listSpaces: function () {
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return persistenceService.listSpaces();
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},
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/**
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* List all objects in a specific space.
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* @memberof CachingPersistenceDecorator#
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* @param {string} space the space in which to list objects
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* @returns {Promise.<string[]>} keys for objects in this space
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* @memberof platform/persistence/cache.CachingPersistenceDecorator#
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*/
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listObjects: function (space) {
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return persistenceService.listObjects(space);
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},
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/**
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* Create an object in a specific space. This will
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* be cached to expedite subsequent retrieval.
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* @memberof CachingPersistenceDecorator#
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* @param {string} space the space in which to create the object
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* @param {string} key the key associate with the object for
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* subsequent lookup
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* @param {object} value a JSONifiable object to store
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* @returns {Promise.<boolean>} an indicator of the success or
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* failure of this request
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* @memberof platform/persistence/cache.CachingPersistenceDecorator#
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*/
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createObject: function (space, key, value) {
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addToCache(space, key, value);
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return persistenceService.createObject(space, key, value);
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},
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/**
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* Read an object from a specific space. This will read from a
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* cache if the object is available.
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* @memberof CachingPersistenceDecorator#
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* @param {string} space the space in which to create the object
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* @param {string} key the key which identifies the object
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* @returns {Promise.<object>} a promise for the object; may
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* resolve to undefined (if the object does not exist
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* in this space)
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* @memberof platform/persistence/cache.CachingPersistenceDecorator#
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*/
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readObject: function (space, key) {
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return (cache[space] && cache[space][key]) ?
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fastPromise(cache[space][key].value) :
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persistenceService.readObject(space, key)
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.then(putCache(space, key));
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},
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/**
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* Update an object in a specific space. This will
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* be cached to expedite subsequent retrieval.
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* @memberof CachingPersistenceDecorator#
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* @param {string} space the space in which to create the object
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* @param {string} key the key associate with the object for
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* subsequent lookup
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* @param {object} value a JSONifiable object to store
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* @returns {Promise.<boolean>} an indicator of the success or
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* failure of this request
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* @memberof platform/persistence/cache.CachingPersistenceDecorator#
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*/
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updateObject: function (space, key, value) {
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return persistenceService.updateObject(space, key, value)
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.then(function (result) {
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addToCache(space, key, value);
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return result;
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});
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},
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/**
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* Delete an object in a specific space. This will
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* additionally be cleared from the cache.
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* @memberof CachingPersistenceDecorator#
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* @param {string} space the space in which to create the object
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* @param {string} key the key associate with the object for
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* subsequent lookup
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* @param {object} value a JSONifiable object to delete
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* @returns {Promise.<boolean>} an indicator of the success or
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* failure of this request
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* @memberof platform/persistence/cache.CachingPersistenceDecorator#
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*/
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deleteObject: function (space, key, value) {
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if (cache[space]) {
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delete cache[space][key];
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}
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return persistenceService.deleteObject(space, key, value);
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then: function (callback) {
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return fastPromise(callback(value));
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}
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};
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}
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// Update the cached instance of an object to a new value
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function replaceValue(valueHolder, newValue) {
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var v = valueHolder.value;
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// If it's a JS object, we want to replace contents, so that
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// everybody gets the same instance.
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if (typeof v === 'object' && v !== null) {
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// Only update contents if these are different instances
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if (v !== newValue) {
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// Clear prior contents
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Object.keys(v).forEach(function (k) {
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delete v[k];
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});
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// Shallow-copy contents
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Object.keys(newValue).forEach(function (k) {
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v[k] = newValue[k];
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});
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}
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} else {
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// Otherwise, just store the new value
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valueHolder.value = newValue;
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}
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}
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// Place value in the cache for space, if there is one.
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CachingPersistenceDecorator.prototype.addToCache = function (space, key, value) {
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var cache = this.cache;
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if (cache[space]) {
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if (cache[space][key]) {
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replaceValue(cache[space][key], value);
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} else {
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cache[space][key] = { value: value };
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}
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}
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};
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// Create a function for putting value into a cache;
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// useful for then-chaining.
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CachingPersistenceDecorator.prototype.putCache = function (space, key) {
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var self = this;
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return function (value) {
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self.addToCache(space, key, value);
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return value;
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};
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};
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CachingPersistenceDecorator.prototype.listSpaces = function () {
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return this.persistenceService.listSpaces();
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};
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CachingPersistenceDecorator.prototype.listObjects = function (space) {
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return this.persistenceService.listObjects(space);
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};
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CachingPersistenceDecorator.prototype.createObject = function (space, key, value) {
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this.addToCache(space, key, value);
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return this.persistenceService.createObject(space, key, value);
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};
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CachingPersistenceDecorator.prototype.readObject = function (space, key) {
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var cache = this.cache;
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return (cache[space] && cache[space][key]) ?
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fastPromise(cache[space][key].value) :
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this.persistenceService.readObject(space, key)
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.then(this.putCache(space, key));
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};
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CachingPersistenceDecorator.prototype.updateObject = function (space, key, value) {
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var self = this;
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return this.persistenceService.updateObject(space, key, value)
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.then(function (result) {
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self.addToCache(space, key, value);
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return result;
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});
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};
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CachingPersistenceDecorator.prototype.deleteObject = function (space, key, value) {
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if (this.cache[space]) {
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delete this.cache[space][key];
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}
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return this.persistenceService.deleteObject(space, key, value);
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};
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return CachingPersistenceDecorator;
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}
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);
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