由孩子一对多找到亲戚

Question

I have this classes:

class Parent{
    static hasMany = [children:Child]
}

class Children{
    static belongsTo = [Parent]
}

I want to do something like

Parent.findByChildren(ChildInstance)

In the database there is a table with the relationship id's, but I don't know how to access to it.

But that doesn't work, which is the proper way?

Thanks

Answer 1

Change your Children class belongsTo clause :

class Children{
    static belongsTo = [parent: Parent]
}

This will allow you to access a child's parent instance : childInstance.parent

Answer 2

First I would change the relationship in Children domain to

static belongsTo = [parent: Parent]  // suggested by @bassmartin

or

Parent parent

both does the same thing.

Once you have the ChildInstance and the reference to the parent, you can simply do

ChildInstance.parent     // returns instance of parent

Similarly, if you want to find all the children of a parent, you can do

parent.children          // return an array of children which you can iterate over.