On Aug 19, 3:31 pm, jhaagmans [email protected] wrote:
this thread, particularly the part where I explained that nested sets
can do what acts_as_tree cannot: get all descendants (no matter how
deep) with a single database query. There is no way to do that at all
Now look at the example I gave here earlier in this thread. I’ve used
it and it generates exactly as many queries as my acts_as_tree (which
is based on his example). Not one less. So, what’s that guy doing
wrong? I can’t figure it out and yes, I’ve looked into the rdoc.
I finally looked at the example you provided, and I can see why you’re
confused. That’s a horrible example. This guy is using
awesome_nested_set as if it were acts_as_tree: only going one level
into the tree with each query (which is why he’s calling
@category.children each time). Doing it that way, you’re absolutely
right that there’s no real advantage over acts_as_tree
But that’s not how awesome_nested_set should be used for maximum
benefit. What you should be doing is something like
@root.descendants . That will – with a single query – load all
descendants of @root, to infinite depth, into memory. Then you can
play with them in memory without touching the database again until you
need to save something.
Okay, but again: why? The same story as the previous one? If I can do
all this with one query, I would like to know how.
See above. Try methods like descendants, watch the SQL, and observe
the real power of the data stricture.
And I would like to
know how I can get the sortable functionality to work with
acts_as_nested_set. You said I should use acts_as_list, but doesn’t
that make the lft and rgt columns obsolete?
Not really. acts_as_list (at least, the way I use it with
awesome_nested_set) only deals with ordering among siblings. lft and
rgt, however, contain information that also deals with parent/child
However, you may not need acts_as_list, since unlike acts_as_tree,
siblings in nested-set trees do have an implied ordering.
And then again, what’s the
advantage of using acts_as_nested_set?
It describes the tree structure. acts_as_list explicitly does not.
I’ll look into it, but chances are I’m not getting this to work with
the scarce information available on the net.
It’s not even that difficult. Just spend your time on understanding
the concept rather than looking for examples. (That said, if I find a
good example, I’ll let you know.)
No. awesome_nested_set should not make your controller or views any
harder to understand. If anything, it should make them easier to
understand, because you do not have to do lots of database queries to
retrieve the records you need.
Then I’ve caught a bad example. The problem is: it’s the -only- real
example I could find! And I really need examples to figure these kinds
of things out!
As I said above, you’ve caught a terrible example. Drop it and
start from scratch. Look at the rdoc again, in particular the README
and the InstanceMethods page. Don’t be afraid to check out the source
either; it’s very clearly written. You’ll be using the children and
descendants methods a lot; these do what you’d expect from their