View source for Using nested sets

==Adding a New Node==
Adding a new node to the table is done in a similar way to adding a row to a normal Joomla table. Data is bound to the Joomla table object using the bind method, followed by calls to check and store. These methods have been overridden in the ''JTableNested'' class to provide the additional functionality required for storing nested sets.

However, in order to determine where in the tree the new node is to be inserted, you need to make a call to the ''setLocation'' method. The ''setLocation'' method takes two arguments. The first is the id of a "reference" node in the tree. The new node will be inserted relative to this node with the relationship being specified by the second argument. Possible values for this relationship are:
* '''before''' - the new node will be inserted before the reference node but at the same level.
* '''after''' - the new node will be inserted after the reference node but at the same level.
* '''first-child''' - the new node will be inserted as the first child node of the reference node.
* '''last-child''' - the new node will be inserted as the last child node of the reference node.

In this example a new node is inserted as the first child of the reference node.
<syntaxhighlight lang="php">
// Given an array of data fields in $data_array and a reference node id in $reference_id,
// this code will add the new node as the first child of the reference node.

// Get the table object.
// Note that in a model you can replace this with $table = $this->getTable();
$table = JTable::getInstance('yourtable');

// Specify where to insert the new node.
$table->setLocation($reference_id, 'first-child');

// Bind data to the table object.
$table->bind($data_array);

// Force a new node to be created.
$table->id = 0;

// Check that the node data is valid.
$table->check();

// Store the node in the database table.
$table->store();
</syntaxhighlight>
In order to maintain the integrity of the data structure, the table is locked during a node insertion operation. Adding a new node to a large table is an expensive operation so the table could potentially be locked for a considerable period. Take this into account when designing your application.