Grails / GORM: How to remove a relation from a M:N relation when deleting an entity?

[Kai Wähner]

Hi,

I have the following situation: A project has several employees. An employee is assigned to several projects. There is no "belongsTo"-cascade because if I delete a project or
an employee, I do not want to delete the other one, of course. Two questions:

1) How do I remove the relations in the table project_employee if I delete the employee? If I use the "belongsTo"-cascade, then the table project_employee would be empty, but the project
would be deleted, too ?!
Do I have to do it manually by getting all projects of the employee,
and then remove the employee from every employee-list of each project? There should be an easier way?

2) A project has sub-projects (self referencing hasMany-relationship). The sub-project also has a M:N relation to employees. I want to realize a constraint, so that
an employee may only be within a sub-project if he is also assigned to the main project. How do I realize this constraint?

Thanks a lot for help...

Best regards, Kai

[Gregg Bolinger]

I find it kind of difficult to follow you. The best thing would be to show us your domain classes to compliment your description of the problem.

[Kai Wähner]

Ok, I will explain with the domain classes.

   
class Projekt {

    String name


    static belongsTo = [client : Client, projekt: Projekt]

    // Employee is M:N, the others are 1:N
    static hasMany = [subprojekte: Projekt, employee: Employee]
    }
    
    

    
class Employee {
    
    String name
   

    // define the owner of the M:N-relation
    static belongsTo = [projekt: Projekt]

    // M:N-relation
    static hasMany = [projekte: Projekt]
    
    }
 

These domains create these tables: "projekt", "employee", "project_employee" for the M:N relationship, and "project_subproject"

1) How do I delete an employee and the entries within project_employee, but not the project?

2) Project has Sub-Projects. I need a constraint, so that an employee may only be member of a sub-project, if it also is a member in the main project already.


I hope you can follow me now, viewing the two domains?