GORM Relations without dependent delete

Question

I have two domain classes User and Node. The following conditions should hold.

a User can have zero or one node
a Node can have one to n User (it is always initialized with a User instance)
if you delete a Node the User will not be deleted
if you delete a User the reference in the Node will be deleted

I tried:

class User {
   Node node
}

class Node {

  // constructor
  Node(User user) {
    addToUsers(user)
    save()
  }  

  hasMany = [users: User]
}

The former does not work. It does not work because when you delete a node there is a dependent reference in the user instance that will not be delete automatically.

How can I model the domain classes in this case?

What happens to the User table? The node_id can't possibly exist if there is a foreign key when the Node is deleted. — James Kleeh, Nov 01 '13 at 17:01

score 2 · Accepted Answer · answered Nov 08 '13 at 12:59

Use a join table like this:

class User {
    Set<Node> getNodes() {
        UserNode.executeQuery("select x.node from UserNode x where x.user = :user", [user: this])
    }

    def addToNodes(Node node) {
       def userNode = new UserNode()
       userNode.user = this
       userNode.node = node
       userNode.save()      
    }
}


class Node {
      Set<User> getUsers() { ... }
}

class UserNode {
   User user
   Node node
}

ataylor · Answer 2 · 2013-10-29T20:38:19.523

0

Mark node as nullable and add a cascade mapping to the User class, specifying what operations you want to be cascaded:

class User {
    Node node

    static constraints = {
        node nullable: true
    }

    static mapping = {
        node cascade: 'save-update,delete'
    }

}

edited Oct 29 '13 at 20:38

answered Oct 29 '13 at 20:32

ataylor

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But I do not want the node to be deleted if one user is deleted. I want the node to be deleted if there are no more users associated to the node. – Michael Oct 30 '13 at 00:11

GORM Relations without dependent delete

2 Answers2

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