How to deal with async. findOrCreate method for passport and mongoose

问题

Authentication module 'Passport' requires a FindOrCreate method in order to do a login. I am using mongoose in order to save my users with the following schema:

var UserSchema = new Schema({
    firstname: String,
    lastname: String,
    email: String,
    accounts: []
});

The accounts array holds objects that represent facebook accounts, like {provider: "facebook", uid: "someFacebookId"}.

My authentication strategy looks like this:

// Authentication Strategy
passport.use(new FacebookStrategy({
    clientID: CONFIG.fb.appId,
    clientSecret: CONFIG.fb.appSecret,
    callbackURL: CONFIG.fb.callbackURL
  },
  function(accessToken, refreshToken, profile, done) {
    // asynchronous verification, for effect...
    process.nextTick(function () {

      User.find({ 'accounts.uid': profile.id, 'accounts.provider': 'facebook' }, function(err, olduser) {

          if(olduser._id) {
            console.log('User: ' + olduser.firstname + ' ' + olduser.lastname + ' found and logged in!');
            done(null, olduser);
          } else {
            var newuser = new User();
            var account = {provider: "facebook", uid: profile.id};
            newuser.accounts.push(account);
            newuser.firstname = profile.name.givenName;
            newuser.lastname = profile.name.familyName;
            newuser.email = "TBD...";

            newuser.save(function(err) {
              if(err) { throw err; }
              console.log('New user: ' + newuser.firstname + ' ' + newuser.lastname + ' created and logged in!');
              done(null, newuser);
            });
          }
        });
    });
  }
));

Problem: After querying my database (User.find(...)) the callback function is executed immediately without waiting for my database to answer. This results in a undefined olduser object. So I am getting a dublicate of the same user into my database every time this user tries to login.

How do I handle this asynchronous callback properly?

回答1:

User.find returns an array of documents that match your conditions. In your case you want to use User.findOne instead, and then check if (olduser)... to determine if a matching doc was found.

回答2:

Hate to nitpick, but the other methods mentioned here break if two users try to signup at the same time-- before you go into production, you'll want to have a look into transactions: http://www.mongodb.org/display/DOCS/two-phase+commit

回答3:

process.nextTick(function () {
      var query = User.findOne({ 'fbId': profile.id });
      query.exec(function (err, oldUser) {
        console.log(oldUser);
        if(oldUser) {
          console.log('User: ' + oldUser.name + ' found and logged in!');
          done(null, oldUser);
        } else {
          var newUser = new User();
          newUser.fbId = profile.id;
          newUser.name = profile.displayName;
          newUser.email = profile.emails[0].value;

          newUser.save(function(err) {
            if(err) {throw err;}
            console.log('New user: ' + newUser.name + ' created and logged in!');
            done(null, newUser);
          }); 
        }
      });
    });

回答4:

There's an app for that: mongoose-findorcreate

来源：https://stackoverflow.com/questions/11155108/how-to-deal-with-async-findorcreate-method-for-passport-and-mongoose