Merge pull request #779 from ably/once-array

EventEmitter: add EventEmitter#once(event[], ...)

common/lib/util/eventemitter.js

@@ -186,7 +186,16 @@ var EventEmitter = (function() {
 		} else if(Utils.isEmptyArg(event)) {
 			this.anyOnce.push(listener);
 		} else if(Utils.isArray(event)){
-			throw("Arrays of events can only be used with on(), not once()");
+			var listenerWrapper = function() {
+				var args = Array.prototype.slice.call(arguments);
+				Utils.arrForEach(event, function(ev) {
+					self.off(ev, listenerWrapper);
+				});
+				listener.apply(this, args);
+			};
+			Utils.arrForEach(event, function(ev) {
+				self.on(ev, listenerWrapper);
+			});
 		} else {
 			var listeners = (this.eventsOnce[event] || (this.eventsOnce[event] = []));
 			listeners.push(listener);

spec/realtime/event_emitter.test.js

@@ -342,6 +342,31 @@ define(['shared_helper', 'chai'], function (helper, chai) {
 			closeAndFinish(done, realtime);
 		});
 
+		it('arrayOfEventsWithOnce', function (done) {
+			var realtime = helper.AblyRealtime({ autoConnect: false }),
+				callbackCalled = 0,
+				eventEmitter = realtime.connection;
+
+			var callback = function (arg) {
+				callbackCalled += 1;
+				expect(arg).to.equal('expected');
+			};
+
+			try {
+				callbackCalled = 0;
+				eventEmitter.once(['a', 'b', 'c'], callback);
+				eventEmitter.emit('a', 'expected');
+				eventEmitter.emit('b', 'wrong');
+				eventEmitter.emit('c', 'wrong');
+				expect(callbackCalled).to.equal(1, 'listener called back only once, for the first event emitted');
+			} catch (err) {
+				closeAndFinish(done, realtime, err);
+				return;
+			}
+
+			closeAndFinish(done, realtime);
+		});
+
 		/* check that listeners added in a listener cb are not called during that
 		 * emit instance */
 		it('listenerAddedInListenerCb', function (done) {