How to verify if a Meteor.user username exists? - meteor

Question

I'm building a messenger application, and before a conversation is created I want to verify if a user exists. If it does, then it will create the conversation. If not, then it should return an error. I've been working with this code on the server side but for some reason it won't work. I've tried many different tweaks, but this is basically my structure:
Meteor.methods({
createConversation: function(secondPerson) {
function doesUserExist(secondPerson) {
var userx = Meteor.users.findOne({username: secondPerson});
if (userx === secondPerson) {
return false;
} else {
return true;
}
}
if (doesUserExist()) {
Conversations.insert({
person1: Meteor.user().username,
person2: secondPerson
});
} else {
Conversations.insert({
person1: "didn't work"
});
}
}
});

Answer 1

The main point you were missing is that find returns a cursor, whereas findOne returns a document. Here is one way to implement the method:
Meteor.methods({
createConversation: function(username) {
check(username, String);
if (!this.userId) {
throw new Meteor.Error(401, 'you must be logged in!');
}
if (Meteor.users.findOne({username: username})) {
return Conversations.insert({
person1: Meteor.user().username,
person2: username
});
} else {
throw new Meteor.Error(403, username + " does not exist!");
}
}
});
Note the following features:
validates that username is a string
requires that the user be logged in to create a conversation
reduces the user existence check to a single line
returns the id of the new conversation
uses Meteor.Error with explanations which can be seen on the client
To use it just open your browser console and try making calls like:
Meteor.call('createConversation', 'dweldon', function(err, id){console.log(err, id);});