// Problem: The association Post -> User is working, the other way round not:

groovy:000> u = new User(name:'hoschi', password:'secret').save()
===> com.hubbub.User : 1
groovy:000> t = new Tag(name:'my_tag', user:u).save()
===> com.hubbub.Tag : 1
groovy:000> p = new Post(tags:[t], user:u, content: 'Post content').save()
===> com.hubbub.Post : 1
groovy:000> p.user
===> com.hubbub.User : 1
groovy:000> u.posts
===> null

// User

class User {
  static hasMany    = [ posts : Post, tags : Tag, following : User ]

  String name
  String password
  Profile profile
  //....
}

// Post

class Post {
  static belongsTo = [user:User]
  static hasMany = [tags : Tag]
}