Creating a web service and a web service function
Moodle 2.0
WORK IN PROGRESS
In this document you will learn how to create a web service function.
This document expect that you first read the administration manual Setting_up_a_web_service.
To explain how to write a new web service function, we will write a web service function create_groups($groups). This function create a group into a Moodle course.
This function will take a list of group object as parameters and it will return the same groups with their newly created id. If ever one group creation fails, the function will throw an exception, and no creation will happen.
We'll finally add the web service function to a core web service.
Preparation
Identify:
- core function(s) you need to call (or/and write) : groups_create_group() from /group/lib.php
- 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.
