Way to handle circular references

[daemonfire300]

If I have 2 tables referencing each other like:

Group: id, owner
User: id, group

If I use the classical PostGet hook, I end up with an infinite loop of callbacks.

[coopernurse]

In theory if you use SelectOne with a pointer to an existing value you could wire things bi-directionally. This issue would depend on resolution of #164 Then you could do something like:

type Group struct {
    Id string 
    //  not sure how you're mapping this, I'm assuming it's wired manually
    User User  `db:"-"`
}

func (me *Group) PostGet(ex SqlExecutor) error {
  if me.User.Id == "" {
     me.User.Group = *me
     return ex.SelectOne(&me.User, "select * from User where GroupId=?", me.Id)
  }
  return nil
}

type User struct {
    Id string
    Group Group  `db:"-"`
}

func (me *User) PostGet(ex SqlExecutor) error {
  if me.Group.Id == "" {
     me.Group.User = *me
     return ex.SelectOne(&me.Group, "select * from Group where UserId=?", me.Id)
  }
  return nil
}

Would that work? Again, due to #164 that code won't work today, but once fixed it should work.

[daemonfire300]

Imagine: I call Select(User{}) this will call PostGet on the User, which will cal Select(Group{}) which will call PostGet on Group which will call Select(User{}), this can not be handled by the PostGet or Object itself, because the PostGet is called automatically when fetching the first object.

[daemonfire300]

https://github.com/coopernurse/gorp/blob/develop/gorp.go#L1438-L1468
Just needs to use an internal map with pointers to the objects and a flag so it can check for circular references.