Issue #1948566 by joachim: Document batch API callbacks using new standard

includes/form.inc

@@ -4256,7 +4256,7 @@ function element_validate_number($element, &$form_state) {
  * returns any user input in the 'results' or 'message' keys of $context,
  * it must also sanitize them first.
  *
- * Sample batch operations:
+ * Sample callback_batch_operation():
  * @code
  * // Simple and artificial: load a node of a given type for a given user
  * function my_function_1($uid, $type, &$context) {
@@ -4308,7 +4308,7 @@ function element_validate_number($element, &$form_state) {
  * }
  * @endcode
  *
- * Sample 'finished' callback:
+ * Sample callback_batch_finished():
  * @code
  * function batch_test_finished($success, $results, $operations) {
  *   // The 'success' parameter means no fatal PHP errors were detected. All
@@ -4347,12 +4347,14 @@ function element_validate_number($element, &$form_state) {
  * @param $batch_definition
  *   An associative array defining the batch, with the following elements (all
  *   are optional except as noted):
- *   - operations: (required) Array of function calls to be performed.
+ *   - operations: (required) Array of operations to be performed, where each
+ *     item is an array consisting of the name of an implementation of
+ *     callback_batch_operation() and an array of parameter.
  *     Example:
  *     @code
  *     array(
- *       array('my_function_1', array($arg1)),
+ *       array('callback_batch_operation_1', array($arg1)),
- *       array('my_function_2', array($arg2_1, $arg2_2)),
+ *       array('callback_batch_operation_2', array($arg2_1, $arg2_2)),
  *     )
  *     @endcode
  *   - title: A safe, translated string to use as the title for the progress
@@ -4364,10 +4366,10 @@ function element_validate_number($element, &$form_state) {
  *     @elapsed. Defaults to t('Completed @current of @total.').
  *   - error_message: Message displayed if an error occurred while processing
  *     the batch. Defaults to t('An error has occurred.').
- *   - finished: Name of a function to be executed after the batch has
+ *   - finished: Name of an implementation of callback_batch_finished(). This is
- *     completed. This should be used to perform any result massaging that may
+ *     executed after the batch has completed. This should be used to perform
- *     be needed, and possibly save data in $_SESSION for display after final
+ *     any result massaging that may be needed, and possibly save data in
- *     page redirection.
+ *     $_SESSION for display after final page redirection.
  *   - file: Path to the file containing the definitions of the 'operations' and
  *     'finished' functions, for instance if they don't reside in the main
  *     .module file. The path should be relative to base_path(), and thus should

modules/system/form.api.php

@@ -0,0 +1,126 @@
+<?php
+
+/**
+ * @file
+ * Calbacks provided by the form system.
+ */
+
+/**
+ * @addtogroup callbacks
+ * @{
+ */
+
+/**
+ * Perform a single batch operation.
+ *
+ * Callback for batch_set().
+ *
+ * @param $MULTIPLE_PARAMS
+ *   Additional parameters specific to the batch. These are specified in the
+ *   array passed to batch_set().
+ * @param $context
+ *   The batch context array, passed by reference. This contains the following
+ *   properties:
+ *   - 'finished': A float number between 0 and 1 informing the processing
+ *     engine of the completion level for the operation. 1 (or no value
+ *     explicitly set) means the operation is finished: the operation will not
+ *     be called again, and execution passes to the next operation or the
+ *     callback_batch_finished() implementation. Any other value causes this
+ *     operation to be called again; however it should be noted that the value
+ *     set here does not persist between executions of this callback: each time
+ *     it is set to 1 by default by the batch system.
+ *   - 'sandbox': This may be used by operations to persist data between
+ *     successive calls to the current operation. Any values set in
+ *     $context['sandbox'] will be there the next time this function is called
+ *     for the current operation. For example, an operation may wish to store a
+ *     pointer in a file or an offset for a large query. The 'sandbox' array key
+ *     is not initially set when this callback is first called, which makes it
+ *     useful for determining whether it is the first call of the callback or
+ *     not:
+ *     @code
+ *       if (empty($context['sandbox'])) {
+ *         // Perform set-up steps here.
+ *       }
+ *     @endcode
+ *     The values in the sandbox are stored and updated in the database between
+ *     http requests until the batch finishes processing. This avoids problems
+ *     if the user navigates away from the page before the batch finishes.
+ *   - 'message': A text message displayed in the progress page.
+ *   - 'results': The array of results gathered so far by the batch processing.
+ *     This array is highly useful for passing data between operations. After
+ *     all operations have finished, this is passed to callback_batch_finished()
+ *     where results may be referenced to display information to the end-user,
+ *     such as how many total items were processed.
+ */
+function callback_batch_operation($MULTIPLE_PARAMS, &$context) {
+  if (!isset($context['sandbox']['progress'])) {
+    $context['sandbox']['progress'] = 0;
+    $context['sandbox']['current_node'] = 0;
+    $context['sandbox']['max'] = db_query('SELECT COUNT(DISTINCT nid) FROM {node}')->fetchField();
+  }
+
+  // For this example, we decide that we can safely process
+  // 5 nodes at a time without a timeout.
+  $limit = 5;
+
+  // With each pass through the callback, retrieve the next group of nids.
+  $result = db_query_range("SELECT nid FROM {node} WHERE nid > %d ORDER BY nid ASC", $context['sandbox']['current_node'], 0, $limit);
+  while ($row = db_fetch_array($result)) {
+
+    // Here we actually perform our processing on the current node.
+    $node = node_load($row['nid'], NULL, TRUE);
+    $node->value1 = $options1;
+    $node->value2 = $options2;
+    node_save($node);
+
+    // Store some result for post-processing in the finished callback.
+    $context['results'][] = check_plain($node->title);
+
+    // Update our progress information.
+    $context['sandbox']['progress']++;
+    $context['sandbox']['current_node'] = $node->nid;
+    $context['message'] = t('Now processing %node', array('%node' => $node->title));
+  }
+
+  // Inform the batch engine that we are not finished,
+  // and provide an estimation of the completion level we reached.
+  if ($context['sandbox']['progress'] != $context['sandbox']['max']) {
+    $context['finished'] = $context['sandbox']['progress'] / $context['sandbox']['max'];
+  }
+}
+
+/**
+ * Complete a batch process.
+ *
+ * Callback for batch_set().
+ *
+ * This callback may be specified in a batch to perform clean-up operations, or
+ * to analyze the results of the batch operations.
+ *
+ * @param $success
+ *   A boolean indicating whether the batch has completed successfully.
+ * @param $results
+ *   The value set in $context['results'] by callback_batch_operation().
+ * @param $operations
+ *   If $success is FALSE, contains the operations that remained unprocessed.
+ */
+function callback_batch_finished($success, $results, $operations) {
+  if ($success) {
+    // Here we do something meaningful with the results.
+    $message = t("!count items were processed.", array(
+      '!count' => count($results),
+      ));
+    $message .= theme('item_list', array('items' => $results));
+    drupal_set_message($message);
+  }
+  else {
+    // An error occurred.
+    // $operations contains the operations that remained unprocessed.
+    $error_operation = reset($operations);
+    $message = t('An error occurred while processing %error_operation with arguments: @arguments', array(
+      '%error_operation' => $error_operation[0],
+      '@arguments' => print_r($error_operation[1], TRUE)
+    ));
+    drupal_set_message($message, 'error');
+  }
+}