Tree¶

Adding data¶

In the previous section, we used existing data and checked that it looked hierarchal via the method generatetreelist. However, usually you would add your data in exactly the same way as you would for any model. For example:

// pseudo controller code
$data['Category']['parent_id'] =  3;
$data['Category']['name'] =  'Skating';
$this->Category->save($data);

When using the tree behavior its not necessary to do any more than set the parent_id, and the tree behavior will take care of the rest. If you don’t set the parent_id, the tree behavior will add to the tree making your new addition a new top level entry:

// pseudo controller code
$data = array();
$data['Category']['name'] =  'Other People\'s Categories';
$this->Category->save($data);

Running the above two code snippets would alter your tree as follows:

• My Categories

  • Fun

    • Sport

      • Surfing

      • Extreme knitting

      • Skating New

    • Friends

      • Gerald

      • Gwendolyn

  • Work

    • Reports

      • Annual

      • Status

    • Trips

      • National

      • International

• Other People’s Categories New

Modifying data¶

Modifying data is as transparent as adding new data. If you modify something, but do not change the parent_id field - the structure of your data will remain unchanged. For example:

// pseudo controller code
$this->Category->id = 5; // id of Extreme knitting
$this->Category->save(array('name' =>'Extreme fishing'));

The above code did not affect the parent_id field - even if the parent_id is included in the data that is passed to save if the value doesn’t change, neither does the data structure. Therefore the tree of data would now look like:

• My Categories

  • Fun

    • Sport

      • Surfing

      • Extreme fishing Updated

      • Skating

    • Friends

      • Gerald

      • Gwendolyn

  • Work

    • Reports

      • Annual

      • Status

    • Trips

      • National

      • International

• Other People’s Categories

Moving data around in your tree is also a simple affair. Let’s say that Extreme fishing does not belong under Sport, but instead should be located under Other People’s Categories. With the following code:

// pseudo controller code
$this->Category->id = 5; // id of Extreme fishing
$newParentId = $this->Category->field('id', array('name' => 'Other People\'s Categories'));
$this->Category->save(array('parent_id' => $newParentId));

As would be expected the structure would be modified to:

• My Categories

  • Fun

    • Sport

      • Surfing

      • Skating

    • Friends

      • Gerald

      • Gwendolyn

  • Work

    • Reports

      • Annual

      • Status

    • Trips

      • National

      • International

• Other People’s Categories

  • Extreme fishing Moved

Deleting data¶

The tree behavior provides a number of ways to manage deleting data. To start with the simplest example; let’s say that the reports category is no longer useful. To remove it and any children it may have just call delete as you would for any model. For example with the following code:

// pseudo controller code
$this->Category->id = 10;
$this->Category->delete();

The category tree would be modified as follows:

• My Categories

  • Fun

    • Sport

      • Surfing

      • Skating

    • Friends

      • Gerald

      • Gwendolyn

  • Work

    • Trips

      • National

      • International

• Other People’s Categories

  • Extreme fishing

Querying and using your data¶

Using and manipulating hierarchical data can be a tricky business. In addition to the core find methods, with the tree behavior there are a few more tree-orientated permutations at your disposal.

Most tree behavior methods return and rely on data being sorted by the lft field. If you call find() and do not order by lft, or call a tree behavior method and pass a sort order, you may get undesirable results.

$allChildren = $this->Category->children(1); // a flat array with 11 items
// -- or --
$this->Category->id = 1;
$allChildren = $this->Category->children(); // a flat array with 11 items

// Only return direct children
$directChildren = $this->Category->children(1, true); // a flat array with 2 items

$totalChildren = $this->Category->childCount(1); // will output 11
// -- or --
$this->Category->id = 1;
$directChildren = $this->Category->childCount(); // will output 11

// Only counts the direct descendants of this category
$numChildren = $this->Category->childCount(1, true); // will output 2

array(
    [1] =>  "My Categories",
    [2] =>  "_Fun",
    [3] =>  "__Sport",
    [4] =>  "___Surfing",
    [16] => "___Skating",
    [6] =>  "__Friends",
    [7] =>  "___Gerald",
    [8] =>  "___Gwendolyn",
    [9] =>  "_Work",
    [13] => "__Trips",
    [14] => "___National",
    [15] => "___International",
    [17] => "Other People's Categories",
    [5] =>  "_Extreme fishing"
)

$parent = $this->Category->getparentnode(2); //<- id for fun
// $parent contains All categories

$parents = $this->Category->getpath(15);

// contents of $parents
array(
    [0] =>  array('Category' => array('id' => 1, 'name' => 'My Categories', ..)),
    [1] =>  array('Category' => array('id' => 9, 'name' => 'Work', ..)),
    [2] =>  array('Category' => array('id' => 13, 'name' => 'Trips', ..)),
    [3] =>  array('Category' => array('id' => 15, 'name' => 'International', ..)),
)

moveDown¶

Used to move a single node down the tree. You need to provide the ID of the element to be moved and a positive number of how many positions the node should be moved down. All child nodes for the specified node will also be moved.

Here is an example of a controller action (in a controller named Categories) that moves a specified node down the tree:

function movedown($name = null, $delta = null) {
        $cat = $this->Category->findByName($name);
        if (empty($cat)) {
            $this->Session->setFlash('There is no category named ' . $name);
            $this->redirect(array('action' => 'index'), null, true);
        }

        $this->Category->id = $cat['Category']['id'];

        if ($delta > 0) {
            $this->Category->moveDown($this->Category->id, abs($delta));
        } else {
            $this->Session->setFlash('Please provide the number of positions the field should be moved down.');
        }

        $this->redirect(array('action' => 'index'), null, true);
    }

For example, if you’d like to move the “Sport” category one position down, you would request: /categories/movedown/Sport/1.

moveUp¶

Used to move a single node up the tree. You need to provide the ID of the element to be moved and a positive number of how many positions the node should be moved up. All child nodes will also be moved.

Here’s an example of a controller action (in a controller named Categories) that moves a node up the tree:

function moveup($name = null, $delta = null){
        $cat = $this->Category->findByName($name);
        if (empty($cat)) {
            $this->Session->setFlash('There is no category named ' . $name);
            $this->redirect(array('action' => 'index'), null, true);
        }

        $this->Category->id = $cat['Category']['id'];

        if ($delta > 0) {
            $this->Category->moveup($this->Category->id, abs($delta));
        } else {
            $this->Session->setFlash('Please provide a number of positions the category should be moved up.');
        }

        $this->redirect(array('action' => 'index'), null, true);

    }

For example, if you would like to move the category “Gwendolyn” up one position you would request /categories/moveup/Gwendolyn/1. Now the order of Friends will be Gwendolyn, Gerald.

removeFromTree¶

removeFromTree($id=null, $delete=false)

Using this method wil either delete or move a node but retain its sub-tree, which will be reparented one level higher. It offers more control than delete(), which for a model using the tree behavior will remove the specified node and all of its children.

Taking the following tree as a starting point:

• My Categories

  • Fun

    • Sport

      • Surfing

      • Extreme knitting

      • Skating

Running the following code with the id for ‘Sport’

$this->Node->removeFromTree($id);

The Sport node will be become a top level node:

• My Categories

  • Fun

    • Surfing

    • Extreme knitting

    • Skating

• Sport Moved

This demonstrates the default behavior of removeFromTree of moving the node to have no parent, and re-parenting all children.

If however the following code snippet was used with the id for ‘Sport’

$this->Node->removeFromTree($id,true);

The tree would become

• My Categories

  • Fun

    • Surfing

    • Extreme knitting

    • Skating

This demonstrates the alternate use for removeFromTree, the children have been reparented and ‘Sport’ has been deleted.

reorder¶

This method can be used to sort hierarchical data.