MEAN Stack: How to update a function's result

问题:

I'm having a commenting system and I need to store the upvotes in the database whenever the upvote icon is clicked. The function I have increases the number but as soon as I refresh it, it says 0 again. How do I store it directly to the database? Here is the code:

In the ang.js in the public/javascripts directory:

var app=angular.module('peopleComments',['ui.router']);
app.factory('comments',['$http', function($http){
var c={
comments:[]
};

//loading all existing comments with getAll()
c.getAll=function(){
return $http.get('/comments').success(function(data){
    angular.copy(data, c.comments);
});
};

//function which creates the new comments for updating in the database
c.create = function(comment) {
return $http.post('/comments', comment).success(function(data){
c.comments.push(data);
});};
return c;
}]);

app.controller('Base',[
'$scope','comments',function($scope,comments){
  $scope.comments=comments.comments;

    $scope.addComment=function(){
        if(!$scope.username||$scope.username==''){$scope.username='Anonymous';}
        if(!$scope.contents||$scope.contents==''){return;}
        comments.create({
            username: $scope.username,
            contents: $scope.contents,
            });
        $scope.username='';
        $scope.contents='';
    }
$scope.increaseUpvotes=function(comment){   //function which updates the upvotes
  comment.upvotes+=1;
}

}]);

回答1:

You need to create a c.update(comment) method in your service that takes a comment to update and then calls a corresponding $http.put() method in your API to update the comment when the upvote button is clicked.

Update: One more potential issue - if you are not specifically creating a comment.upvotes property and setting it to 0 by default then your comment.upvotes += 1 might be adding one to null or undefined and not really adding one.