Added ability to pass results from one callback to another

ArtS · Jan 7, 2011 · ad16382 · ad16382
1 parent 09621f5
commit ad16382
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Showing 2 changed files with 60 additions and 12 deletions.
diff --git a/index.js b/index.js
@@ -8,8 +8,8 @@ function defaultErrorHandler(err) {
 function runChain(chain, index) {
     var chainIndex = index || 0,
         currentElem,
-        currArgs = [],
-        argIndex = 0;
+        argIndex = 0,
+        currentArgs = [];
 
     if (!chain || chain.length === 0) {
         return;
@@ -24,7 +24,10 @@ function runChain(chain, index) {
     function checkErrorCallback(err) {
 
         var handler,
-            msg;
+            msg,
+            args,
+            resultArgs,
+            i = 0;
 
         if (err) {
             // If error handler callback is provided, call it supplying 'err' object,
@@ -35,19 +38,35 @@ function runChain(chain, index) {
         }
 
         chainIndex += 1;
-        runChain(chain, chainIndex);
-    }
+        debugger;
+        args = [chain, chainIndex];
 
-    // Add pre-defined arguments
-    if (currentElem.args) {
-        for (; argIndex < currentElem.args.length; argIndex++) {
-            currArgs.push(currentElem.args[argIndex]);
+        // If passResultToNextStep was specified, need to pass result of previous callback
+        // to next function in chain, skipping the 'err' object
+        if (currentElem.passResultToNextStep) {
+            resultArgs = Array.prototype.splice.apply(arguments, [1, arguments.length-1]);
+            for (; i < resultArgs.length; i++) {
+                args.push(resultArgs[i]);
+            }
         }
+
+        runChain.apply(null, args);
     }
 
-    currArgs.push(checkErrorCallback);
+    if (arguments.length > 2) {
+        // Looks like we were supplied agruments from previous call.
+        // Let's take away 'chain' and 'chainIndex' arguments and pass it on further
+        // down the call chain
+        currentArgs = Array.prototype.splice.apply(arguments, [2, arguments.length-2]);
+    } else {
+        // No arguments from prevous call, just use pre-defined arguments, if any
+        if (currentElem.args) {
+            currentArgs = currentElem.args.slice();
+        }
+    }
 
-    currentElem.target.apply(this, currArgs);
+    currentArgs.push(checkErrorCallback);
+    currentElem.target.apply(this, currentArgs);
 }
 
 

diff --git a/tests.js b/tests.js
@@ -150,7 +150,7 @@ chain = [
         target: function(a, b, c, callback) {
             test_args.push([a, b, c]);
             test_stack.push(3);
-            callback(null);
+            callback(null, a, b, c);
         },
         args: [7, 8, 9]
     }
@@ -163,3 +163,32 @@ assertArraysEqual(chain[0].args, test_args[0]);
 assertArraysEqual(chain[1].args, test_args[1]);
 assertArraysEqual(test_stack, [1, 2]);
 assertEquals(ERROR_MESSAGE, test_error);
+
+
+//
+// 5. Test passing of callback results to the next function inthe chain
+//
+test_stack = [];
+test_args = [];
+
+chain = [
+    {
+        target: function(callback) {
+            test_stack.push(1);
+            callback(null, 1, 2, 3);
+        },
+        passResultToNextStep: true
+    },
+    {
+        target: function(a, b, c) {
+            test_stack.push(2);
+            test_args.push([a, b, c]);
+            //callback(null);
+        }
+    }
+];
+
+c.runChain(chain);
+
+assertArraysEqual(test_stack, [1, 2]);
+assertArraysEqual(test_args[0], [1, 2, 3]);