Pushing a contact (tested against mongoose 2.3.11)

contact.coffee

 #!/usr/bin/env coffee

global.mongoose = require 'mongoose'
mongoose.connect 'mongodb://localhost/test'

Schema         = mongoose.Schema

User = new Schema
   userId         : { type: String, index: true, required: true }
   contacts       : [ { type: Schema.ObjectId, ref: 'User' } ]

User = mongoose.model('User', User)

User.remove {}, (err) -> console.log(err) if err
console.log "- cleaning out existing users"

userIds = [ 'A', 'B', 'C', 'D' ]
userA = null
numRoles = userIds.length

userIds.forEach (userId,index) ->
  User.create { userId: userId }, (err, user) ->
    if err then console.log err

    console.log "+ creating user: #{user.userId}"
    userA = user if user.userId is 'A'

    if --numRoles <= 0
       console.log(userA)

       User.update {userId: { $ne: 'A'}}, { $push: { contacts: userA } }, ->
         if err then console.log err
         User.find {}, (err, users) ->
            if err then console.log err
            console.log(users) # users B,C,D should have user A in their contacts
            process.exit()