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

$treelist = $this->Category->generatetreelist();

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.

If the node is the last child, or is a top level node with no subsequent node this method will return false.

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.

If the node is the first child, or is a top level node with no previous node this method will return false.

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() Sessions, 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:

<?php
$this->Node->removeFromTree($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’:

<?php
$this->Node->removeFromTree($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¶

reorder ( array('id' => null, 'field' => $Model->displayField, 'order' => 'ASC', 'verify' => true) )

Reorders the nodes (and child nodes) of the tree according to the field and direction specified in the parameters. This method does not change the parent of any node:

<?php
$model->reorder(array(
    'id' => ,    //id of record to use as top node for reordering, default: $Model->id
    'field' => , //which field to use in reordering, default: $Model->displayField
    'order' => , //direction to order, default: 'ASC'
    'verify' =>  //whether or not to verify the tree before reorder, default: true
));

If you have saved your data or made other operations on the model, you might want to set $model->id = null before calling reorder. Otherwise only the current node and it’s children will be reordered.

Recover¶

recover(&$model, $mode = 'parent', $missingParentAction = null)

The mode parameter is used to specify the source of info that is valid/correct. The opposite source of data will be populated based upon that source of info. E.g. if the MPTT fields are corrupt or empty, with the $mode 'parent' the values of the parent_id field will be used to populate the left and right fields. The missingParentAction parameter only applies to “parent” mode and determines what to do if the parent field contains an id that is not present.

Available $mode options:

• 'parent' - use the existing parent_id‘s to update the lft and rght fields
• 'tree' - use the existing lft and rght fields to update parent_id

Available missingParentActions options when using mode='parent':

• null - do nothing and carry on
• 'return' - do nothing and return
• 'delete' - delete the node
• int - set the parent_id to this id

// Rebuild all the left and right fields based on the parent_id
$this->Category->recover();
// or
$this->Category->recover('parent');

// Rebuild all the parent_id's based on the lft and rght fields
$this->Category->recover('tree');

Reorder¶

reorder(&$model, $options = array())

Reorders the nodes (and child nodes) of the tree according to the field and direction specified in the parameters. This method does not change the parent of any node.

Reordering affects all nodes in the tree by default, however the following options can affect the process:

• 'id' - only reorder nodes below this node.
• 'field‘ - field to use for sorting, default is the displayField for the model.
• 'order' - 'ASC' for ascending, 'DESC' for descending sort.
• 'verify' - whether or not to verify the tree prior to resorting.

$options is used to pass all extra parameters, and has the following possible keys by default, all of which are optional:

array(
    'id' => null,
    'field' => $model->displayField,
    'order' => 'ASC',
    'verify' => true
)

Verify¶

verify(&$model)

Returns true if the tree is valid otherwise an array of errors, with fields for type, incorrect index and message.

Each record in the output array is an array of the form (type, id, message)

• type is either 'index' or 'node'
• 'id' is the id of the erroneous node.
• 'message' depends on the error

$this->Categories->verify();

Example output:

Array
(
    [0] => Array
        (
            [0] => node
            [1] => 3
            [2] => left and right values identical
        )
    [1] => Array
        (
            [0] => node
            [1] => 2
            [2] => The parent node 999 doesn't exist
        )
    [10] => Array
        (
            [0] => index
            [1] => 123
            [2] => missing
        )
    [99] => Array
        (
            [0] => node
            [1] => 163
            [2] => left greater than right
        )

)