Merge pull request #2 from endeepak/master

callbacks generated by MULTI can include an identifier which can subsequently be used to distinguish results

README.md

@@ -173,6 +173,21 @@ Here is an example of `this.MULTI()` in action (repeated from the overview):
 		}
 	);
 
+  You can identify the results of a function by passing a result identifier to MULTI. The results of a function can retrieved using this key in the final step. The result will be a single value if callback receives 0 or 1 argument, otherwise it will be an array of arguments passed to the callback.
+
+  Example:
+
+	flow.exec(
+		function() {
+			dbGet('userIdOf:bobvance', this.MULTI('bob'));
+			dbGet('userIdOf:joohndoe', this.MULTI('john'));
+		},function(results) {
+		  dbSet('user:' + results['bob'] + ':email', 'bobvance@potato.egg');
+		  dbSet('user:' + results['john'] + ':email', 'joohndoe@potato.egg');
+		  okWeAreDone();
+		}
+	);
+
 In many cases, you may simply discard the arguments passed to each of the callbacks generated
 by `this.MULTI()`, but if you need them, they are accessible as an array of `arguments`
 objects passed as the first argument of the next function. Each `arguments` object will be

examples/keystore.js

@@ -31,6 +31,14 @@ exports.get = function(key, callback) {
 	}, 100);
 }
 
+// keystore.exists(key, callback)
+// callback signature: (value)
+exports.exists = function(key, callback) {
+	setTimeout(function() {
+		if (callback) callback(key in db);
+	}, 100);
+}
+
 // keystore.increment(key, incrementBy, callback)
 // callback signature: (error, newValue)
 exports.increment = function(key, incrementBy, callback) {

flow.js

@@ -58,11 +58,17 @@
 			// MULTI can be used to generate callbacks that must ALL be called before the next step
 			// in the flow is executed. Arguments to those callbacks are accumulated, and an array of
 			// of those arguments objects is sent as the one argument to the next step in the flow.
-			flowState.MULTI = function() {
+			// @param {String} resultId An identifier to get the result of a multi call.
+			flowState.MULTI = function(resultId) {
 				flowState.__multiCount += 1;
 				return function() {
 					flowState.__multiCount -= 1;
 					flowState.__multiOutputs.push(arguments);
+
+          if (resultId) {
+            var result = arguments.length <= 1 ? arguments[0] : arguments
+            flowState.__multiOutputs[resultId] = result;
+          }
 
 					if (flowState.__multiCount === 0) {
 						var multiOutputs = flowState.__multiOutputs;

tests.js

@@ -4,7 +4,7 @@ var keystore = require('./examples/keystore');
 
 var flowsComplete = 0;
 setTimeout(function() {
-	var expected = 3;
+	var expected = 5;
 	assert.strictEqual(flowsComplete, expected, flowsComplete + "/" + expected +" flows finished");
 }, 1000);
 
@@ -34,6 +34,35 @@ flow.exec(
 	}
 );
 
+// MULTI with result identifier test
+flow.exec(
+  function() {
+    var db = keystore.getDb();
+    db['firstName'] = "Bob"
+    db['lastName'] = "Vance"
+    keystore.get("firstName", this.MULTI('first-name'));
+    keystore.get("lastName", this.MULTI('last-name'));
+  },function(results) {
+    assert.strictEqual(results['first-name'][1], "Bob", "multi with result identifier test didn't work");
+    assert.strictEqual(results['last-name'][1], "Vance", "multi with result identifier test didn't work");
+    flowsComplete += 1;
+  }
+);
+
+// MULTI with result identifier for single return value test
+flow.exec(
+  function() {
+    var db = keystore.getDb();
+    db['bob'] = "Bob Vance"
+    keystore.exists("bob", this.MULTI('bob-exists'));
+    keystore.exists("john", this.MULTI('john-exists'));
+  },function(results) {
+    assert.strictEqual(results['bob-exists'], true, "multi with result identifier for single return value test didn't work");
+    assert.strictEqual(results['john-exists'], false, "multi with result identifier for single return value test didn't work");
+    flowsComplete += 1;
+  }
+);
+
 // serialForEach test
 var valueSequence = [];
 flow.serialForEach([1, 2, 3, 4], function(val) {