Domas monkus drupal module development

Overview Drupal’s components Modules APIs

Drupal module development
Basics and examples

Domas Monkus
domas@monkus.lt :: http://domas.monkus.lt

25th September 2010
Drupal camp Riga


Domas Monkus


What is drupal?

CMS
Node system
Taxonomy
CCK & Views


What is drupal?

CMS FRAMEWORK
Node system Module Architecture
Taxonomy Theming
CCK & Views APIs


Drupal development workﬂow
Where did my time go?


Should You develop a custom module?


Considerations
Not-invented-here?

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


Considerations
Not-invented-here?

Investment - making custom one-oﬀ modules is not overly
cost-eﬀective. Will you need it again? In the foreseeable
future?


Considerations
Not-invented-here?

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


Alternatives
To custom modules

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


Alternatives
To custom modules

Extending similar modules - base your work on a tested
codebase.


Alternatives
To custom modules

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


Enough talk
Let’s get to the programming

Things you need to know:
Drupal’s architecture
Drupal module structure
Drupal core subsystems and APIs
Coding conventions


Enough talk
Let’s get to the programming

Things you need to know:
Drupal module structure
Drupal core subsystems and APIs
Coding conventions
Things you REALLY need to know:
PHP
MySQL
HTML, CSS
javascript (probably)


Overview



procedural (and it works!)
event driven
hooks


Hooks
Drupal’s glue

Observer pattern
Drupal calls available hooks at certain points
Modules implement hooks
Hooks add additional processing of requests


Hooks
There’s how many?!

(D7 has 178 hooks)


Hooks
What they do.


Drupal’s APIs
Output

Theming
Menu API
Output ﬁltering
Image manipulation
Blocks
Translations
Search


Drupal’s APIs
Input

Forms API
XMLRPC


Drupal’s APIs
Users

User management
Session handling
Access control


Drupal’s APIs
Storage

Database abstraction layer
File storage
Caching


Drupal’s APIs
Infrastructure

Batch API
Email handling
Updates
Module system


Reference

http://api.drupal.org


How does this work?


Hooking things together
Delayed publishing

Problem
We need to publish nodes of unveriﬁed users not immediately, but
after a certain wait period.


Delayed publishing

Problem
We need to publish nodes of unveriﬁed users not immediately, but
after a certain wait period.

Hooks used
hook_perms
To deﬁne a permission ’Publish nodes immediately’.
hook_nodeapi
To forcefully unpublish new nodes.
hook_cron
To publish nodes whose wait period has already passed.


Term-node synchronization

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


Term-node synchronization

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

Hooks used
hook_form_alter
To add options to taxonomy vocabulary edit form.
hook_taxonomy
To react to term creation, updates and deletes.
hook_node_info
To deﬁne a custom node type.
hook_insert, hook_update, hook_delete
To 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 description
module_name.install - installation/uninstallation
* module_name.module - module code


The .info ﬁle

name = Devel
description = Various blocks, pages..
package = Development
dependencies[] = menu
core = 6.x


The .module ﬁle

A simple php ﬁle
Hooks 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

Tasks
routing
menus
breadcrumbs


Menu API
An 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

Tasks
Form creation and rendering
Form altering
Processing
Form validation and security


Form API
What’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 API
Altering forms

Any Form API form can be altered by other modules
Fields can be added, removed or changed
Additional validation and submit processing can be added


Form API
hook_form_alter

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

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


Form API
An 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

Tasks
React to all operations on nodes
Additional processing or validation of node ﬁelds
Add additional content to nodes on load


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

$node
The node object
$op
The operation being performed
$a3, $a4
Additional parameters, dependant on operation


Node API
Operations

load
insert
update
delete
validate
presave
etc.


Node API
An 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 module
cache operations, dummy content generation, debugging aids
coder module
coding standards validation, basic module security tips
drupal api module
have a local instance of api.drupal.org
simpletest module
automated unit testing of your module (highly encouraged)
version control
cvs, svn, git, mercurial - anything is better than nothing


Tips

Coding practices
Coding standards
keep your code clean and documented - if you ever decide to
release it
Caching
because performance matters
Splitting large module ﬁles
parts can be loaded on demand - less load on the system

Looking for help
#drupal
go to the irc.freenode.net irc channel for help
api.drupal.org
complete reference of drupal core APIs


.. and never


.. and never
ever


.. and never
ever
hack


.. and never
ever
hack
core


Don’t hack core!


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


Questions?

Domas monkus drupal module development

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