Last updated April 16, 2011. Created by naught101 on April 16, 2011.
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Entity revisioning is fairly simple - most of it is handled by field API, so you just need to implement a revision table, and appropriate load and save functions, and add an {example_revision} table with the appropriate columns.
hook_schema implementation
<?php
/**
* Implements hook_schema().
*/
function example_schema() {
$schema['example'] = array(
'description' => 'Keeps track of example entities.',
'fields' => array(
'example_id' => array(
'type' => 'serial',
'unsigned' => TRUE,
'not null' => TRUE,
'description' => 'Unique example id.',
),
'vid' => array(
'description' => 'The current {example_revision}.vid version identifier.',
'type' => 'int',
'unsigned' => TRUE,
'not null' => TRUE,
'default' => 0,
),
'created' => array(
'description' => 'The Unix timestamp when the example was created.',
'type' => 'int',
'not null' => TRUE,
'default' => 0,
),
'changed' => array(
'description' => 'The Unix timestamp when the example was most recently saved.',
'type' => 'int',
'not null' => TRUE,
'default' => 0,
),
// .. Any other columns you need in for your entity
),
'primary key' => array('example_id'),
);
$schema['example_revision'] = array(
'description' => 'Keeps track of example entities.',
'fields' => array(
'example_id' => array(
'type' => 'int',
'unsigned' => TRUE,
'not null' => TRUE,
'default' => 0,
'description' => 'Unique example id (entity id).',
),
'vid' => array(
'description' => 'The current {example_revision}.vid version identifier.',
'type' => 'serial',
'unsigned' => TRUE,
'not null' => TRUE,
),
'changed' => array(
'description' => 'The Unix timestamp when the example was most recently saved.',
'type' => 'int',
'not null' => TRUE,
'default' => 0,
),
// Any other columns that you have in the example entity table that you
// want to store in revisions.
),
'primary key' => array('example_id', 'vid'),
);
}
?>Add a _save function
This assumes your entites being saved are stdClass objects, with an entity ID, a created date, and any other data that you want to push into the database. New entities to be saved should also have a property called "is_new" set to TRUE.
<?php
function example_save($example) {
if ($example->is_new) {
// Adds the data to the entity table, and returns the new $example_id:
$example_id = db_insert('example')
->useDefaults(array('example_id'))
->fields(array(
'created' => REQUEST_TIME,
'changed' => REQUEST_TIME,
// Any other DB columns that you want to provide defaults for.
))
->execute();
// Add the new entity ID back into the entity object
$example->example_id = $example_id;
// Add a revision for all new nodes.
$example->revision = TRUE;
}
if (!empty($example->revision)) {
// Add the entity data to the revision table, and return the unique revision id.
$vid = db_insert('example_revision')
->useDefaults(array('vid'))
->fields(array(
'example_id' => $example->example_id,
// We don't need to store the creation time
'changed' => REQUEST_TIME,
// Any other DB columns that you want to store, and for which you
// need revisioning.
))
->execute();
// Add the revision ID back to the entity
$example->vid = $vid;
// Update the revision ID on the entity table.
db_update('example')
->condition('example_id', $example->example_id)
->fields(array(
'vid' => $example->vid,
))
->execute();
}
// let Field UI deal with the fields.
if ($example->is_new) {
field_attach_insert('example', $example);
}
else {
field_attach_update('example', $example);
}
return $example->example_id;
}
?>
Comments
hook_entity_presave, _insert, and _update?
Who invokes the hooks?
Drupal doesn't invoke the hooks, so you have to invoke the hooks.
Entity API provide them by default
http://drupal.org/node/878804
Or you can create your custom Entity Controller.
The Simple Module Example
If you want a practical module as a reference, you won't regret to checkout one of productions of the Drupal Genius(merlinofchaos): http://drupal.org/project/fieldable_panels_panes