delete all items from sorted set in grails

Question

I have a grails project with a class that I can delete no problem when doing it "manually" from the controller. I use the following code.

def delete = {
    def projectInstance = Project.get( params.id )
    def employee = projectInstance.employee
    def projectarray = new ArrayList<Project>();
    projectarray += employee.getProjects()
    println("Size of projectarray is " + projectarray.size())
    if(projectInstance) {
        def rolearray = []

        projectarray.remove(projectInstance)
        def temp = new TreeSet<Project>();
        temp += employee.getProjects()
        temp.clear()
        temp.addAll(projectarray)
        employee.projects = temp

        projectInstance.employer = null
        projectInstance.delete(flush:true)
        flash.message = "Project ${params.id} deleted"
        redirect(action:"edit", controller: "employee", id: employee.id)
    }
    else {
        flash.message = "Project not found with id ${params.id}"
        redirect(action:list)
    }
}

So that deletes a single instance fine.

Now i want to, from a different controller, remove ALL projects from an employee.

This is stored in the employee like so:

class Employee implements Comparable
{
static hasMany = [projects:Project]  
static constraints = 
{
}

static mapping = {
    projects cascade:"all-delete-orphan", lazy:false
}

@XmlElementWrapper(name="projectslist")
SortedSet<Project> projects = new TreeSet<Project>();  // make a sortedSet?

}

So how would I now delete all projects from a particular employee instance?

Answer 1

You could use the removeFrom* method that is generated by Grails when you declare the hasMany relationship - it's the equivalent of the addTo* methods:

def employee = Employee.get(params.id)
employee.projects.toList().each { employee.removeFromProjects(it) } // toList() prevents a ConcurrentModifactionException

Answer 2

I might be misunderstanding your question because I can't make sense of some of your code. It seems unnecessary. If your relationships are setup correctly (i.e. Project belongsTo Employee), this should be sufficient to delete a single project:

def delete = {
    def projectInstance = Project.get( params.id )
    projectInstance.delete(flush:true)
    flash.message = "Project ${params.id} deleted"
    redirect(action:"edit", controller: "employee", id: employee.id)
}

If this is a one-to-many, the next time you retrieve the employee the project will be gone. And this should work to delete all projects of an employee:

def delete = {
    def employee = Employee.get( params.id )
    employee.getProjects().clear()
    employee.save(flash:true)
    flash.message = "All projects of employee deleted."
    redirect(action:"edit", controller: "employee", id: employee.id)
}

That assumes cascade:"all-delete-orphan". If that's not the case then you might need to also delete the instances and that might look something like this:

def delete = {
    def employee = Employee.get( params.id )

    // Make copy to avoid concurrent modification issues later
    def copy = new TreeSet<Project>(employee.getProjects()); 

    employee.getProjects().clear();
    employee.save(flash:true)

    copy.each{
      $it.delete();
    }     

    flash.message = "All projects of employee deleted."
    redirect(action:"edit", controller: "employee", id: employee.id)
}

I'm not a groovy expert, so not sure if the copy is needed, or if you can just iterate on the collection directly. Seems like there is always a groovier way to do things. You might also want to check out the deleteFrom dynamic domain class method. That might be a more efficient grails approach depending on number of relationships to be deleted.