在grails中定义一对多和多对多关系

Question

i have two domain : User and Task such as :

1) a user can be the author of many tasks

2) a user can participate in many tasks,in the same time,a task can have many users which participate in

so,i want to define a one-to-many for 1) and a many-to-many for 2)

User{
  static hasMany = [createdTasks : Task,  //for one-to-many
                    assignedTasks : Task  //for many-to-many
                   ]

  static mappedBy = [createdTasks : author]

}

Task{

  User author
  static hasMany = [assignedUsers : User]// for many-to-many


}

i think i have to define the owner side of my many-to-many relationship(assignedTasks-assgnedUsers) ? anyone have a idea for defining the correct relationship satisfying my specification 1) and 2)?

thanks :)

Answer 1

I think you could accomplish this an easier way:

Really the relationships can just be on the task. The only reason to do what you are trying to do is to create a bi-directional relationship. This can be achieved simpler with declaring methods on the user to get the objects you want.

User{
   Set<Task> getCreatedTasks() {
     Task.findAllByAuthor(this)
   }

   Set<Task> getAssignedTasks() {
     Task.executeQuery("""
       Select t
       from Task t join t.assignedUsers as tu
       where tu = :user
     """, [user: this])
   }
}

Task{
  User author
  static hasMany = [assignedUsers : User]
}

Answer 2

Try this. Note the quotation in mappedBy.

User {
  static hasMany = [
    createdTasks: Task, // for one-to-many
    assignedTasks: Task // for many-to-many
  ]
  static mappedBy = [
    createdTasks: 'author'
  ]
}

Task {
  User author
  static hasMany = [
    assignedUsers: User // for many-to-many
  ]
  static belongsTo = [
    User
  ]
}