domas monkus drupal module development

Overview Drupal’s components Modules APIs

Drupal module developmentBasics and examples

Domas [email protected] :: http://domas.monkus.lt

25th September 2010Drupal camp Riga


Domas Monkus


What is drupal?

CMSNode systemTaxonomyCCK & Views

FRAMEWORKModule ArchitectureThemingAPIs


Drupal development workflowWhere did my time go?


Should You develop a custom module?


ConsiderationsNot-invented-here?

Maintenance - you will need to maintain and update even ifyou do not release it.

Investment - making custom one-off modules is not overlycost-effective. Will you need it again? In the foreseeablefuture?Lonely path - it takes time to flush out all the bugs. Only inthis case you will almost always be the only one finding them.



Maintenance - you will need to maintain and update even ifyou do not release it.Investment - making custom one-off modules is not overlycost-effective. Will you need it again? In the foreseeablefuture?

Lonely path - it takes time to flush out all the bugs. Only inthis case you will almost always be the only one finding them.



Maintenance - you will need to maintain and update even ifyou do not release it.Investment - making custom one-off modules is not overlycost-effective. Will you need it again? In the foreseeablefuture?Lonely path - it takes time to flush out all the bugs. Only inthis case you will almost always be the only one finding them.


AlternativesTo custom modules

Contrib - over 4500 modules, are you sure your problemhasn’t been tackled?

Extending similar modules - base your work on a testedcodebase.One-off solutions - if it’s a rare problem, sometimes hacksare not the worst idea.



Contrib - over 4500 modules, are you sure your problemhasn’t been tackled?Extending similar modules - base your work on a testedcodebase.

One-off solutions - if it’s a rare problem, sometimes hacksare not the worst idea.



Contrib - over 4500 modules, are you sure your problemhasn’t been tackled?Extending similar modules - base your work on a testedcodebase.One-off solutions - if it’s a rare problem, sometimes hacksare not the worst idea.


Enough talkLet’s get to the programming

Things you need to know:

Drupal’s architectureDrupal module structureDrupal core subsystems and APIsCoding conventions

Things you REALLY need to know:PHPMySQLHTML, CSSjavascript (probably)


Overview


Drupal’s architecture

procedural (and it works!)event drivenhooks


HooksDrupal’s glue

Observer patternDrupal calls available hooks at certain pointsModules implement hooksHooks add additional processing of requests


HooksThere’s how many?!

(D7 has 178 hooks)


HooksWhat they do.


Drupal’s APIsOutput

ThemingMenu APIOutput filteringImage manipulationBlocksTranslationsSearch


Drupal’s APIsInput

Forms APIXMLRPC


Drupal’s APIsUsers

User managementSession handlingAccess control


Drupal’s APIsStorage

Database abstraction layerFile storageCaching


Drupal’s APIsInfrastructure

Batch APIEmail handlingUpdatesModule system


Reference

http://api.drupal.org


How does this work?


Hooking things togetherDelayed publishing

ProblemWe need to publish nodes of unverified users not immediately, butafter a certain wait period.

Hooks usedhook_permsTo define a permission ’Publish nodes immediately’.hook_nodeapiTo forcefully unpublish new nodes.hook_cronTo publish nodes whose wait period has already passed.


Hooking things togetherTerm-node synchronization

TaskCreate a node for every term in the dictionary and vice-versa,constantly synchronizing the contents of a node’s body and theterm’s description.

Hooks usedhook_form_alterTo add options to taxonomy vocabulary edit form.hook_taxonomyTo react to term creation, updates and deletes.hook_node_infoTo define a custom node type.hook_insert, hook_update, hook_deleteTo react to node creation, updates and deletes.


So where do we put this?


The structure of a drupal module

module_name/* module_name.info - module descriptionmodule_name.install - installation/uninstallation* module_name.module - module code


The .info file

name = Develdescription = Various blocks, pages..package = Developmentdependencies[] = menucore = 6.x


The .module file

A simple php fileHooks and internal functions


The .module file

<?php...define(’DEVEL_ERROR_HANDLER_BACKTRACE’, 2);.../*** Implementation of hook_menu().*/

function devel_menu() {$items = array();$items[’devel/cache/clear’] = array(

’title’ => ’Empty cache’,’page callback’ => ’devel_cache_clear’,’description’ => ’Clear the CSS cache.’,’access arguments’ => array(’access devel information’),’menu_name’ => ’devel’,

);

...


3 most common APIs/hooks


Menu API

Tasksroutingmenusbreadcrumbs


Menu APIAn example

function devel_menu() {$items = array();

$items[’devel/queries’] = array(’title’ => ’Database queries’,’page callback’ => ’devel_queries’,’access callback’ => ’devel_menu_access_store_queries’,’access arguments’ => array(),’menu_name’ => ’devel’,

);

...

return $items;}


Menu API


Form API

TasksForm creation and renderingForm alteringProcessingForm validation and security


Form APIWhat’s in a form?

Forms are defined as nested arrays

$form = array();$form[’mail’] = array(

’#type’ => ’textfield’,’#title’ => t(’Email’),’#size’ => 20,’#maxlength’ => 128,’#required’ => TRUE,

);return drupal_get_form($form);


Form APIAltering forms

Any Form API form can be altered by other modulesFields can be added, removed or changedAdditional validation and submit processing can be added


Form APIhook_form_alter

function hook_form_alter(&$form, $form_state, $form_id)

$formThe form array - passed by reference, can be altered$form_stateThe form’s state (if the form has already been rendered)$form_idThe id of the form being processed


Form APIAn example

function path_form_alter(&$form, $form_state, $form_id) {if (isset($form[’type’]) && isset($form[’#node’])\

&& $form[’type’][’#value’] .’_node_form’ == $form_id) {$path = isset($form[’#node’]->path) ? $form[’#node’]->path : NULL;$form[’path’] = array(

’#type’ => ’fieldset’,’#title’ => t(’URL path settings’),’#collapsible’ => TRUE,’#collapsed’ => empty($path),’#access’ => user_access(’create url aliases’),’#weight’ => 30,

);...


hook_node_api

TasksReact to all operations on nodesAdditional processing or validation of node fieldsAdd additional content to nodes on load


function hook_nodeapi(&$node, $op, $a3 = NULL, $a4 = NULL)

$nodeThe node object$opThe operation being performed$a3, $a4Additional parameters, dependant on operation


Node APIOperations

loadinsertupdatedeletevalidatepresaveetc.


Node APIAn example

function nodeasblock_nodeapi(&$node, $op, $a3 = NULL, $a4 = NULL) {switch ($op) {

case ’load’:$node->nodeasblock = db_result(\

db_query(’SELECT nid FROM {nodeasblock}\WHERE nid = %d’, $node->nid));

break;

case ’insert’:...


Tips and tools


Tools

devel modulecache operations, dummy content generation, debugging aidscoder modulecoding standards validation, basic module security tipsdrupal api modulehave a local instance of api.drupal.orgsimpletest moduleautomated unit testing of your module (highly encouraged)version controlcvs, svn, git, mercurial - anything is better than nothing


Tips

Coding practicesCoding standardskeep your code clean and documented - if you ever decide torelease itCachingbecause performance mattersSplitting large module filesparts can be loaded on demand - less load on the system

Looking for help#drupalgo to the irc.freenode.net irc channel for helpapi.drupal.orgcomplete reference of drupal core APIs


.. and never

everhackcore


.. and neverever

hackcore


.. and nevereverhack

core


.. and nevereverhackcore


Don’t hack core!


That’s it(we’ve barely scratched the surface though)


Questions?

domas monkus drupal module development

Technology

similar modules

custom oneoff modules

oneoff solutions

unpublish new nodes

nodes of unverified

certain wait period

worst idea

rare problem