getDescendants()->having('depth', '=', 2)

[elstamey]

Is it possible to get all of the children at a certain level in the tree? When I recursively use getDescendants() to display the tree, I end up with repeated leaves. But If I could get only the descendants at a certain level, I would be able to recurse without repetition.

[lazychaser]

$node->descendants()->withDepth()->having('depth', 2)->get();

Note that depth is calculated againts a root node, but not the node from which the query has started. At the depth of one are immediate children of the root node.

Tell me if this works.

[elstamey]

$node->descendants()->withDepth()->having('depth', '=', 2)->get();

This worked, but I had to add the = in the having clause.

Thank you very much!

[lazychaser]

I guess this works only when using when.

[elstamey]

I'm still having an issue related to this request. Once I get to a depth of 2, I'm calling the descendants, as we did above, but the descendants being returned seem to include all children at depth=3, which returns one from the wrong parent. I'll try to paste some information to illustrate the problem. Keep in mind, I'm recursively including a blade template, so I am using loops to use the query above.

6 Wordpress - (1 NCSU)
7 Single - (6 Wordpress)
9 intellimedia.ncsu.edu - (7 Single)
10 engr.ncsu.edu - (8 Multi)
8 Multi - (6 Wordpress)

---

On the (7 Single), when I call descendants()->withDepth()->having('depth', '=', 2)->get();
I see the following:

[{"id":"9","label":"intellimedia.ncsu.edu","effective_date":"2014-01-31 15:37:31","created_at":"2014-01-31 15:37:31","updated_at":"2014-01-31 15:37:31","_lft":"12","_rgt":"13","parent_id":"7"},{"id":"10","label":"engr.ncsu.edu","effective_date":"2014-01-31 15:37:31","created_at":"2014-01-31 15:37:31","updated_at":"2014-01-31 15:37:31","_lft":"14","_rgt":"15","parent_id":"8"}]

I hope that this makes sense, as I have explained it. Since the descendants is returning the second one, it is being displayed under Single instead of Multi.

[lazychaser]

I guess you have your tree structure broken. rgt of node with an id of 9 has a value of 13 and node with an id of 10 has a value of 14 for lft, but since they have different parent, they must have at least one node between them.

You have either messed with parent_id and set it explicitly, or you did not enclose manipulations into transaction.

I need to see full database dump to investigate it.

[elstamey]

I haven't begun to manipulate the tree, only have created the tree using the seeder. Here is my ItemsTableSeeder.php

truncate(); // The root node is required NestedSet::createRoot('items', array( 'label' => 'NCSU', 'effective_date' => new DateTime )); $target = Item::root(); $node1 = new Item( array('label' => 'Apps', 'effective_date' => new DateTime) ); $node1->appendTo($target)->save(); $node2 = new Item( array('label' => 'apps.engr.ncsu.edu', 'effective_date' => new DateTime) ); $node2->appendTo($node1)->save(); $node3 = new Item( array('label' => 'apps.wolftech.ncsu.edu', 'effective_date' => new DateTime) ); $node3->appendTo($node1)->save(); $node4 = new Item( array('label' => 'webtools.ncsu.edu', 'effective_date' => new DateTime) ); $node4->appendTo($node1)->save(); $node5 = new Item( array('label' => 'Wordpress', 'effective_date' => new DateTime) ); $node5->appendTo($target)->save(); $node6 = new Item( array('label' => 'Single', 'effective_date' => new DateTime) ); $node6->appendTo($node5)->save(); $node7 = new Item( array('label' => 'Multi', 'effective_date' => new DateTime) ); $node7->appendTo($node5)->save(); $node8 = new Item( array('label' => 'intellimedia.ncsu.edu', 'effective_date' => new DateTime) ); $node8->appendTo($node6)->save(); $node9 = new Item( array('label' => 'engr.ncsu.edu', 'effective_date' => new DateTime) ); $node9->appendTo($node7)->save(); $node10 = new Item( array('label' => 'Custom', 'effective_date' => new DateTime) ); $node10->appendTo($target)->save(); } ``` }

[lazychaser]

Ah, of course. I need to work on this moment. You need to insert node6 before node7.

[elstamey]

I'm sorry, but i don't understand what you meant by "need to work on this moment". Is this an issue or a mistake on my part using your tool?

I have changed the order of my insertions in the seeds file, but it seems like this isn't how it should work. When I use the console, and I add items to the tree out of order, they seem to be placed in the correct tree structure. Am I missing a step in how I am inserting the items in my seeds file? Or is this an issue?

Thank you for your help!
Emily

[lazychaser]

Yes it's an issue, if you read the manual, you can find there that this package is intended to be used once per request when you need to create or update a node. This is because manipulating nodes in nested sets implies updating other nodes in database, which means that already loaded nodes become out of sync with database. You need to refresh target node before inserting into it or insert them in depth-first order (you insert a node, then child of that node, then children of that child, etc).

I need to reconsider the way the nodes are inserted, and I'll do it later.

[elstamey]

Thank you. In the base use case of our application, we will only be inserting/modifying one at a time, so it looks like that will be updated correctly. But if I ever have to rebuild the tree from a backup, I want to be sure that I can do it correctly. In the case of my seeds, when I add an item to a target out of order, I should first find the node I need as my target and then append to it, instead of relying on the object I first used to build that node.

[lazychaser]

Yes, you got it right!