Creating a Comment Service

Because you know you will need a comment service to handle getting and adding comments, you need to add that first. Listing 27.15 implements a comment service that uses the service method. You need to create a function definition called CommentObj. The constructor function accepts the $http service as the only parameter.

You define a getComment() function that accepts commentId and then does a GET request to the /comment/get route to get the full comment data. Notice that this function also accepts a callback function. The callback function returns an error if $http reports one or the comment data from the server.

The addComment() function accepts rootCommentId for the comment thread, parentId for the parent comment, and a newComment parameter that is a JavaScript object with subject and body properties. It then does a POST request to /comment/add to add the new comment to MongoDB. Just as with getComment(), a callback function is executed and returns the results. Then the service is created using the following line to inject $http:

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app.service('commentSrv', ['$http', CommentObj]);

Then you can inject the commentSrv service into your controllers.

Listing 27.15 comment_app.js-commentSrv: Implementing an AngularJS service that provides reusable functionality to get comments from and add new comments to the server

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02 function CommentObj($http) {
03   this.getComment = function(commentId, callback){
04     $http.get('/comments/get', {params: {commentId: commentId}})
05       .success(function(data, status, headers, config) {
06         callback(null, data);
07       })
08       .error(function(data, status, headers, config) {
09         callback(data, {});
10       });
11   };
12   this.addComment = function(rootCommentId, parentId,
13                              newComment, callback){
14     $http.post('/comments/add', { rootCommentId: rootCommentId,
15                                   parentCommentId: parentId,
16                                   newComment: newComment })
17     .success(function(data, status, headers, config) {
18       callback(null, data);
19     })
20     .error(function(data, status, headers, config) {
21     });
22   };
23 }
24 app.service('commentSrv', ['$http', CommentObj]);