Refactor the observer functions into a plugin

lib/model.js

@@ -604,87 +604,8 @@ ModelBaseClass.prototype.setStrict = function (strict) {
   this.__strict = strict;
 };
 
-/**
- * Register an asynchronous observer for the given operation (event).
- * @param {String} operation The operation name.
- * @callback {function} listener The listener function. It will be invoked with
- * `this` set to the model constructor, e.g. `User`.
- * @param {Object} context Operation-specific context.
- * @param {function(Error=)} next The callback to call when the observer
- *   has finished.
- * @end
- */
-ModelBaseClass.observe = function(operation, listener) {
-  if (!this._observers[operation]) {
-    this._observers[operation] = [];
-  }
-
-  this._observers[operation].push(listener);
-};
-
-/**
- * Unregister an asynchronous observer for the given operation (event).
- * @param {String} operation The operation name.
- * @callback {function} listener The listener function.
- * @end
- */
-ModelBaseClass.removeObserver = function(operation, listener) {
-  if (!this._observers[operation]) return;
-
-  var index = this._observers[operation].indexOf(listener);
-  if (index != -1) this._observers[operation].splice(index, 1);
-};
-
-/**
- * Unregister all asynchronous observers for the given operation (event).
- * @param {String} operation The operation name.
- * @end
- */
-ModelBaseClass.clearObservers = function(operation) {
-  if (!this._observers[operation]) return;
-
-  this._observers[operation].length = 0;
-};
-
-/**
- * Invoke all async observers for the given operation.
- * @param {String} operation The operation name.
- * @param {Object} context Operation-specific context.
- * @param {function(Error=)} callback The callback to call when all observers
- *   has finished.
- */
-ModelBaseClass.notifyObserversOf = function(operation, context, callback) {
-  var observers = this._observers && this._observers[operation];
-
-  if (!callback) callback = utils.createPromiseCallback();
-
-  this._notifyBaseObservers(operation, context, function doNotify(err) {
-    if (err) return callback(err, context);
-    if (!observers || !observers.length) return callback(null, context);
-
-    async.eachSeries(
-      observers,
-      function notifySingleObserver(fn, next) {
-        var retval = fn(context, next);
-        if (retval && typeof retval.then === 'function') {
-          retval.then(
-            function() { next(); },
-            next // error handler
-          );
-        }
-      },
-      function(err) { callback(err, context) }
-    );
-  });
-  return callback.promise;
-}
-
-ModelBaseClass._notifyBaseObservers = function(operation, context, callback) {
-  if (this.base && this.base.notifyObserversOf)
-    this.base.notifyObserversOf(operation, context, callback);
-  else
-    callback();
-}
+// Mixin observer
+jutil.mixin(ModelBaseClass, require('./observer'));
 
 jutil.mixin(ModelBaseClass, Hookable);
 jutil.mixin(ModelBaseClass, validations.Validatable);

lib/observer.js

@@ -0,0 +1,92 @@
+var async = require('async');
+var utils = require('./utils');
+
+module.exports = ObserverMixin;
+
+function ObserverMixin() {
+}
+
+/**
+ * Register an asynchronous observer for the given operation (event).
+ * @param {String} operation The operation name.
+ * @callback {function} listener The listener function. It will be invoked with
+ * `this` set to the model constructor, e.g. `User`.
+ * @param {Object} context Operation-specific context.
+ * @param {function(Error=)} next The callback to call when the observer
+ *   has finished.
+ * @end
+ */
+ObserverMixin.observe = function(operation, listener) {
+  this._observers = this._observers || {};
+  if (!this._observers[operation]) {
+    this._observers[operation] = [];
+  }
+
+  this._observers[operation].push(listener);
+};
+
+/**
+ * Unregister an asynchronous observer for the given operation (event).
+ * @param {String} operation The operation name.
+ * @callback {function} listener The listener function.
+ * @end
+ */
+ObserverMixin.removeObserver = function(operation, listener) {
+  if (!(this._observers && this._observers[operation])) return;
+
+  var index = this._observers[operation].indexOf(listener);
+  if (index !== -1) {
+    return this._observers[operation].splice(index, 1);
+  }
+};
+
+/**
+ * Unregister all asynchronous observers for the given operation (event).
+ * @param {String} operation The operation name.
+ * @end
+ */
+ObserverMixin.clearObservers = function(operation) {
+  if (!(this._observers && this._observers[operation])) return;
+
+  this._observers[operation].length = 0;
+};
+
+/**
+ * Invoke all async observers for the given operation.
+ * @param {String} operation The operation name.
+ * @param {Object} context Operation-specific context.
+ * @param {function(Error=)} callback The callback to call when all observers
+ *   has finished.
+ */
+ObserverMixin.notifyObserversOf = function(operation, context, callback) {
+  var observers = this._observers && this._observers[operation];
+
+  if (!callback) callback = utils.createPromiseCallback();
+
+  this._notifyBaseObservers(operation, context, function doNotify(err) {
+    if (err) return callback(err, context);
+    if (!observers || !observers.length) return callback(null, context);
+
+    async.eachSeries(
+      observers,
+      function notifySingleObserver(fn, next) {
+        var retval = fn(context, next);
+        if (retval && typeof retval.then === 'function') {
+          retval.then(
+            function() { next(); },
+            next // error handler
+          );
+        }
+      },
+      function(err) { callback(err, context) }
+    );
+  });
+  return callback.promise;
+}
+
+ObserverMixin._notifyBaseObservers = function(operation, context, callback) {
+  if (this.base && this.base.notifyObserversOf)
+    this.base.notifyObserversOf(operation, context, callback);
+  else
+    callback();
+}