Add single record to mongo collection with meteor - mongodb

Question

I am a new user to JavaScript and the meteor framework trying to understand the basic concepts. First of all I want to add a single document to a collection without duplicate entries.
this.addRole = function(roleName){
console.log(MongoRoles.find({name: roleName}).count());
if(!MongoRoles.find({name: roleName}).count())
MongoRoles.insert({name: roleName});
}
This code is called on the server as well as on the client. The log message on the client tells me there are no entries in the collection. Even if I refresh the page several times.
On the server duplicate entries get entered into the collection. I don't know why. Probably I did not understand the key concept. Could someone point it out to me, please?
Edit-1:
No, autopublish and insecure are not installed anymore. But I already published the MongoRoles collection (server side) and subscribed to it (client side). Furthermore I created a allow rule for inserts (client side).
Edit-2:
Thanks a lot for showing me the meteor method way but I want to get the point doing it without server side only methods involved. Let us say for academic purposes. ;-)
Just wrote a small example:
Client:
Posts = new Mongo.Collection("posts");
Posts.insert({title: "title-1"});
console.log(Posts.find().count());
Server:
Posts = new Mongo.Collection("posts");
Meteor.publish(null, function () {
return Posts.find()
})
Posts.allow({
insert: function(){return true}
})
If I check the server database via 'meteor mongo' it tells me every insert of my client code is saved there.
The log on the client tells me '1 count' every time I refresh the page. But I expected both the same. What am I doing wrong?
Edit-3:
I am back on my original role example (sorry for that). Just thought I got the point but I am still clueless. If I check the variable 'roleCount', 0 is responded all the time. How can I load the correct value into my variable? What is the best way to check if a document exists before the insertion into a collection? Guess the .find() is asynchronous as well? If so, how can I do it synchronous? If I got it right I have to wait for the value (synchronous) because I really relay on it.
Shared environment (client and server):
Roles = new Mongo.Collection("jaqua_roles");
Roles.allow({
insert: function(){return true}
})
var Role = function(){
this.addRole = function(roleName){
var roleCount = Roles.find({name: roleName}).count();
console.log(roleCount);
if(roleCount === 0){
Roles.insert({name: roleName}, function(error, result){
try{
console.log("Success: " + result);
var roleCount = Roles.find({name: roleName}).count();
console.log(roleCount);
} catch(error){
}
});
}
};
this.deleteRole = function(){
};
}
role = new Role();
role.addRole('test-role');
Server only:
Meteor.publish(null, function () {
return Roles.find()
})

Answer 1

Meteor's insert/update/remove methods (client-side) are not a great idea to use. Too many potential security pitfalls, and it takes a lot of thought and time to really patch up any holes. Further reading here.
I'm also wondering where you're calling addRole from. Assuming it's being triggered from client-side only, I would do this:
Client-side Code:
this.addRole = function(roleName){
var roleCount = MongoRoles.find({name: roleName}).count();
console.log(roleCount);
if (roleCount === 0) {
Meteor.call('insertRole', roleName, function (error, result) {
if (error) {
// check error.error and error.reason (if I'm remembering right)
} else {
// Success!
}
});
}
}
How I've modified this code and why:
I made a roleCount variable so that you can avoid calling MongoRoles.find() twice like that, which is inefficient and consumes unneeded resources (CPU, disk I/O, etc). Store it once, then reference the variable instead, much better.
When checking numbers, try to avoid doing things like if (!count). Using if (count === 0) is clearer, and shows that you're referencing a number. Statements like if (!xyz) would make one think this is a boolean (true/false) value.
Always use === in JavaScript, unless you want to intentionally do a loose equality operation. Read more on this.
Always use open/closed curly braces for if and other blocks, even if it contains just a single line of code. This is just good practice so that if you decide to add another line later, you don't have to then wrap it in braces. Just a good practice thing.
Changed your database insert into a Meteor method (see below).
Side note: I've used JavaScript (ES5), but since you're new to JavaScript, I think you should jump right into ES6. ES is short for ECMAScript (which is what JS is based on). ES6 (or ECMAScript 2015) is the most recent stable version which includes all kinds of new awesomeness that JavaScript didn't previously have.
Server-side Code:
Meteor.method('insertRole', function (roleName) {
check(roleName, String);
try {
// Any security checks, such as logged-in user, validating roleName, etc
MongoRoles.insert({name: roleName});
} catch (error) {
// error handling. just throw an error from here and handle it on client
if (badThing) {
throw new Meteor.Error('bad-thing', 'A bad thing happened.');
}
}
});
Hope this helps. This is all off the top of my head with no testing at all. But it should give you a better idea of an improved structure when it comes to database operations.
Addressing your edits
Your code looks good, except a couple issues:
You're defining Posts twice, don't do that. Make a file, for example, /lib/collections/posts.js and put the declaration and instantiation of Mongo.Collection in there. Then it will be executed on both client and server.
Your console.log would probably return an error, or zero, because Posts.insert is asynchronous on the client side. Try the below instead:
.
Posts.insert({title: "title-1"}, function (error, result) {
console.log(Posts.find().count());
});