Parse.com cloud code to prevent users from making duplicate submissions

gistfile1.txt

Parse.Cloud.beforeSave("Requests", function(request, response) {
	var postObj = new Parse.Object("Posts");
	postObj.set("objectId", request.object.get("Post_Pointer"));
	
	var query = new Parse.Query("Requests");
	query.equalTo("Post_Pointer", postObj);
	query.equalTo("Requester", Parse.User.current());
	query.first({
	    success: function(object) {
	        if (object) {
	            response.error("A request has already been submitted.");
	        } else {
	            response.success();
	        }
	    },
	    error: function(error) {
	        response.error("Could not save request. Error: " + error);
	    }
	});
});