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Define access restrictions. This hook allows node modules to limit access to the node types they define.

Parameters

$op The operation to be performed. Possible values:

• “create”
• “delete”
• “update”
• “view”

$node The node on which the operation is to be performed, or, if it does not yet exist, the type of node to be created.
$account A user object representing the user for whom the operation is to be performed.

Return value

TRUE if the operation is to be allowed; FALSE if the operation is to be denied; NULL to not override the settings in the node_access table, or access control modules.

Codes:

function hook_access($op, $node, $account) {
if ($op == 'create') {
return user_access('create my sales', $account);
}

if ($op == 'update' || $op == 'delete') {
if (user_access('edit her sales', $account) && ($account->uid == $node->uid)) {
return TRUE;
}
}
}


Usage sample:
<?php
CREATE TABLE node_sample (
vid int(10) unsigned NOT NULL default '0',
nid int(10) unsigned NOT NULL default '0',
color varchar(255) NOT NULL default '',
quantity int(10) unsigned NOT NULL default '0',
PRIMARY KEY (vid, nid),
KEY `node_sample_nid` (nid))
?>

function node_sample_access($op, $node, $account) {
if ($op == 'create') {
return user_access('create sample content', $account);
}

if ($op == 'update') {
if (user_access('edit any sample content', $account) || (user_access('edit own sample content', $account) && ($account->uid == $node->uid))) {
return TRUE;
}
}

if ($op == 'delete') {
if (user_access('delete any sample content', $account) || (user_access('delete own sample content', $account) && ($account->uid == $node->uid))) {
return TRUE;
}
}
}

In your directory /sites/all/, you have to create 2 sub-directories called “themes” and “modules” where your custom themes and modules are located.

What “hooks” in Drupal is all about? They allow your custom-built modules to interact with the Drupal core.  A hook is a function that is named foo_hookname(), where “foo” is the name of your custom-built module (whose filename is foo.module) and “hookname” is the name of the hook. Each hook has a defined set of parameters and a specified result type.

To extend Drupal system, your custom-built module needs to simply implement a hook. When Drupal wishes to allow intervention from modules, it determines which modules implement a hook and calls that hook in all enabled modules that implement it.

In Drupal 6.x there’re more than 70 hooks that you got to remember in case your internet is down. My next posts will show you how to implement each of these hooks in your custom modules.

Today I have a project from AppraisalWorld that I need to build a module in Drupal. I have known this Drupal CMS since I learned the Joomla Environment but I didn’t have a chance to build many complex modules. So this is an opportunity for me to learn how to build a complex module for Drupal environment.

First, I go to www.drupal.org and read how Drupal works after I install. Then I watched some videos that teach me why and how to use Drupal. Of course, it’s all about the benefits of using Drupal. And then now comes the fun part. I started downloading some contributed modules that you can find here http://drupal.org/project/modules?page=1. You will find tons of contributed modules for Drupal system.

At first, I expected there’s a .sql file like in Joomla and WordPress systems, so I can load to MySQL DB but I keep searching in all folders, I couldn’t find it. So I know that it maybe generating during the installation of the module. Luckily enough, I found a function that use hook_schema() in the file .install. That’s where the table is created in the database. In this function, you have to define a table name, an array of fields, type, length, not null, and default for each table. If you want to add records to database table, build a function that uses hook_update_n and use query “INSERT INTO”.

Each module has to have at least .info and .module files as a mandatory. The .install, or .inc, or .admin.inc, or .tpl.php are just optional depends on how complex your module is.

In the next blog, I will show you how to start with the .info page to get your module going. Stay in tune.