Implementing the CommentThread Model Controller
Listing 27.8 implements the route handling code for the CommentThread model. Two routes are handled: getComment() and addComment(). Due to the size of the file, the code for these two routes is broken down in the following sections.
Implementing the getComment() Route
The getComment() route handler looks up a single CommentThread document, based on the _id field passed in as commentId in the GET request query string.
Listing 27.8 comments_controller.js-getComment: Implementing the route to get comment threads for the Express server
04 exports.getComment = function(req, res) {
05 CommentThread.findOne({ _id: req.query.commentId })
06 .exec(function(err, comment) {
07 if (!comment){
08 res.json(404, {msg: 'CommentThread Not Found.'});
09 } else {
10 res.json(comment);
11 }
12 });
13 };
Implementing the addComment() Route
The addComment() route handler, shown in Listing 27.9, is quite a bit more complex than getComment() and involves a chain of functions to support updating nested comments. The logic flow for adding new comments is as follows:
1. The client sends a request that includes the CommentThread ID, a parent comment ID to add the new comment to, and a JSON object that represents the new comment.
2. The /comment/add route handler calls addComment().
3. The CommentThread object is located using the req.body.rootCommentId value from the POST data.
4. A new Reply object named newComment object is created from the req.body.newComment value from the POST data.
5. addComment() is run recursively, looking through the nested comments until it finds a comment that matches the req.body.parentCommentId passed in from the POST body.
6. The new comment is pushed into the replies array of the parent comment.
7. The updateCommentThread() method uses the following update() operation to update the replies field in the CommentThread document with the one that now contains the updated comment:
CommentThread.update({ _id: commentThread.id },
{$set:{replies:commentThread.replies}}).exec();
8. A success or failure response is sent back to the client.
Listing 27.9 comments_controller.js-addComment: Implementing the addComment() route for the Express server
14 exports.addComment = function(req, res) {
15 CommentThread.findOne({ _id: req.body.rootCommentId })
16 .exec(function(err, commentThread) {
17 if (!commentThread){
18 res.json(404, {msg: 'CommentThread Not Found.'});
19 } else {
20 var newComment = Reply(req.body.newComment);
21 newComment.username = generateRandomUsername();
22 addComment(req, res, commentThread, commentThread,
23 req.body.parentCommentId, newComment);
24 }
25 });
26 };
27 function addComment(req, res, commentThread, currentComment,
28 parentId, newComment){
29 if (commentThread.id== parentId){
30 commentThread.replies.push(newComment);
31 updateCommentThread(req, res, commentThread);
32 } else {
33 for(var i=0; i< currentComment.replies.length; i++){
34 var c = currentComment.replies[i];
35 if (c._id== parentId){
36 c.replies.push(newComment);
37 var replyThread = commentThread.replies.toObject();
38 updateCommentThread(req, res, commentThread);
39 break;
40 } else {
41 addComment(req, res, commentThread, c,
42 parentId, newComment);
43 }
44 }
45 }
46 };
47 function updateCommentThread(req, res, commentThread){
48 CommentThread.update({ _id: commentThread.id },
49 {$set:{replies:commentThread.replies}})
50 .exec(function(err, savedComment){
51 if (err){
52 res.json(404, {msg: 'Failed to update CommentThread.'});
53 } else {
54 res.json({msg: "success"});
55 }
56 });
57 }
Looking at the Comment Model Route Handler
Listing 27.10 shows the full implementation of the comments_controller.js file that provides route handling involving the Comment model. The Comment model route handler code loads the schema for both the CommentThread and Reply models. The CommentThread model provides the ability to look up CommentThread documents as well as update them when new comments are added. The Reply model creates the Reply object when a new comment is added.
The comment controller code provides a function that randomly generates a username for testing purposes:
function generateRandomUsername(){
//typically the username would come from an authenticated session
var users=['DaNae', 'Brad', 'Brendan', 'Caleb', 'Aedan', 'Taeg'];
return users[Math.floor((Math.random()*6))];
}
Typically the username would come from the session in the Request object, but session code is omitted from this example to keep it easier to follow.
Listing 27.10 comments_controller.js: Full implementation of the Comment model route handlers for the Express server
01 var mongoose = require('mongoose'),
02 CommentThread = mongoose.model('CommentThread'),
03 Reply = mongoose.model('Reply'),
04 exports.getComment = function(req, res) {
05 CommentThread.findOne({ _id: req.query.commentId })
06 .exec(function(err, comment) {
07 if (!comment){
08 res.json(404, {msg: 'CommentThread Not Found.'});
09 } else {
10 res.json(comment);
11 }
12 });
13 };
14 exports.addComment = function(req, res) {
15 CommentThread.findOne({ _id: req.body.rootCommentId })
16 .exec(function(err, commentThread) {
17 if (!commentThread){
18 res.json(404, {msg: 'CommentThread Not Found.'});
19 } else {
20 var newComment = Reply(req.body.newComment);
21 newComment.username = generateRandomUsername();
22 addComment(req, res, commentThread, commentThread,
23 req.body.parentCommentId, newComment);
24 }
25 });
26 };
27 function addComment(req, res, commentThread, currentComment,
28 parentId, newComment){
29 if (commentThread.id== parentId){
30 commentThread.replies.push(newComment);
31 updateCommentThread(req, res, commentThread);
32 } else {
33 for(var i=0; i< currentComment.replies.length; i++){
34 var c = currentComment.replies[i];
35 if (c._id== parentId){
36 c.replies.push(newComment);
37 var replyThread = commentThread.replies.toObject();
38 updateCommentThread(req, res, commentThread);
39 break;
40 } else {
41 addComment(req, res, commentThread, c,
42 parentId, newComment);
43 }
44 }
45 }
46 };
47 function updateCommentThread(req, res, commentThread){
48 CommentThread.update({ _id: commentThread.id },
49 {$set:{replies:commentThread.replies}})
50 .exec(function(err, savedComment){
51 if (err){
52 res.json(404, {msg: 'Failed to update CommentThread.'});
53 } else {
54 res.json({msg: "success"});
55 }
56 });
57 }
58 function generateRandomUsername(){
59 //typically the username would come from an authenticated session
60 var users=['DaNae', 'Brad', 'Brendan', 'Caleb', 'Aedan', 'Taeg'];
61 return users[Math.floor((Math.random()*5))];
62 }