Creating a web service and a web service function

Moodle 2.0

First you need to read and execute the administration manual Setting_up_a_web_service. Now you should be more familiar about how web services are set into Moodle.

Preparation

Identify:

• core function(s) you need to call (or/and write)
• the param types that new to be send to your web service function
• the returned value types
• the user capabilities (it most of the time the ones logically required by the core functions)

declare your web service functions/services

All web services function should be declare in the db/services.php of each component. Optionally, any larger services built up of several functions.

$functions = array(

   'moodle_user_create_users' => array(           //web service name (unique in all Moodle)
       'classname'   => 'moodle_user_external', //class containing the function implementation
       'methodname'  => 'create_users',              //name of the function into the class
       'classpath'   => 'user/externallib.php',     //file containing the class (only used for core external function, not needed if your file is 'component/externallib.php'),
       'description' => 'create some users',
       'type' => 'write'
   )

);

//following is optional $services = array(

   'servicename' => array(
       'functions' => array ('functionname', 'secondfunctionname'), //web service function name
       'requiredcapability' => 'some/capability:specified',                  
       'restrictedusers' = >1,
       'enabled'=>0, //used only when installing the services
   )

);

The function name is arbitrary, but it must be globally unique so we highly recommend using the component name as prefix (and "moodle" for core functions).

The actual param description and description of returned values can be obtained from the same class by static method calls by adding '_parameters' and '_returns' to the methodname value.

define your external functions

This example include a function implementation. It has been extracted from the group/externallib.php. This file is a good example of externallib.php files. class moodle_group_external extends external_api { //see following chapter 'function implementation' to have a look to the external_api class

   ...

   public static function add_member($groupid, $userid) {
       $params = self::validate_parameters(self::add_member_parameters(), array('groupid'=>$groupid, 'userid'=>$userid));

       // all the parameter/behavioural checks and security constrainsts go here,
       // throwing exceptions if neeeded and and calling low level (grouplib)
       // add_member() function that will be one in charge of the functionality without
       // further checks.

   }

   ...

}

define your external function description

This example includes param/return value descriptions. It has been extracted from the group/externallib.php. This file is a good example of externallib.php files. class moodle_group_external extends external_api { //see following chapter 'function implementation' to have a look to the external_api class

   public static function add_member_parameters() {
       return new external_function_parameters(
           array(
               'groupid' => new external_value(PARAM_INT, 'some group id'),
               'userid'  => new external_value(PARAM_INT, 'some user id')
           )
       );
   }

   public static function add_member(...) {
       ...
   }

   public static function add_member_returns() {
       return null;
   }

}

test your web service function with default Moodle test client

There is a central test client that can be accessed into webservice/testclient.php In order to add new function to be supported you will need to add a form into webservice/testclient_forms.php. Take example from the other implemented forms.

See also

• Web services
• External services security
• External services description
• Setting_up_a_web_service