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--- local:moodlescript:syntaxspecification [2018/02/27 10:20]
admin [Arguments, identifiers and variables]
+++ local:moodlescript:syntaxspecification [2024/05/14 15:39] (current)
@@ Line 70: / Line 70: @@
    idnumber:JD@35465
    email:john.doe@gmail.com
+=== Special identifier case : identifier given by a function ===
+In some applications, we want an identifier being given by a custom or existing function, depending on some current context. the identifier form will accept the 'func' prefix to identifiy some plugin function to call to get an identifier:
+Example:
+   idnumber:func:local_ent_installer@get_teacher_cat_idnumber
+will invoke the function ''local_ent_installer_get_teacher_cat_idnumber()'' in the plugin ''local_ent_installer' ''locallib.php'' (or by default, ''lib.php'') local library to get the expected identifier. the result of the function will be used as idnumber to find ethe primary identifier of the objet.
+You cannot pass any parameters to this call, so the identifier must be fully determined using current environment globals such as $USER, $COURSE, etc. to compute the expected identifier.
+Here is a sample of an application function that computes the current user's owned category to move a course in:
+    /**
+     * Provides an uniform scheme for a teacher category identifier.
+     * @param object $user a user object. If user is not given will return the cat identifier of
+     * the current user.
+     * @return string
+     */
+    function local_ent_installer_get_teacher_cat_idnumber($user = null) {
+        global $USER;
+        if (is_null($user)) {
+            $user = $USER;
+        }
+        $teachercatidnum = strtoupper($user->lastname).'_'.substr(strtoupper($user->firstname), 0, 1).
+        $teachercatidnum .= '$'.$user->idnumber.'$CAT';
+        return $teachercatidnum;
+     }
+Called in a moodlescript stack context, it will compute the category idnumber of the current user, so we can write a moodlescript move instruction as follows, moving the current course to the adequate destination:
+    MOVE COURSE current TO idnumber:func:local_ent_installer@get_teacher_cat_idnumber
 === Literal Argument ===
@@ Line 97: / Line 134: @@
 Any local invocation of a MoodleScript stack may run the stack with his own global environment variable set, to serve some specific component scoped scripting needs.
-=== Special keywords (metas) ===
+==== Special keywords (metas) ====
+==='current'===
+'current' is a special keyword in place of an expected identifier that will resolve into the nearest current object in the executing environment. F.e, if the expected object is a user identifier, current will resolve to $USER->id. If 'current' addresses a course identifier, it wil usually resolve as $COURSE->id, unless another course id is given to the execution stack by the global context (for plugin developers).
+The use of current will simplify scripts run within a known context, by using shorten expressions:
+   ADD ENROL METHOD guest TO current
+For adding an enrolment method to the current course.
+   ENROL current INTO current AS student
+For enrolling the current user (the $USER being executing the script) into the current course.
+==='last' or 'first'===
+this usually addresses the first available or last available item in the current syntax context. this is used f.e. for blocks location in a region, but might also address any object locaton being sorted with a sortorder attribute.
+==='runtime'===
+Usually identifiers and variable can be evaluated at parse time or at check time, because they are litterals in the script, or they come from some input or global context. But this is not true in all cases. Lets take an example:
+In the following scriptlet:
+   ADD CATEGORY "New category" TO idnumber:EXISTINGCAT HAVING
+   idnumber: NEWCAT
+   MOVE COURSE idnumber:SOMECOURSE TO idnumber:NEWCAT
+We run into an issue because at parse time or at check time, NEWCAT category is not yet created. Thus we must tell the engine that in the second statement, we need the engine waiting the latest moment to evaulate the identifier to move the course in.
+This can be done by the special keywork runtime: and we'll rewrite the scriplet as follows:
+   ADD CATEGORY "New category" TO idnumber:EXISTINGCAT HAVING
+   idnumber: NEWCAT
+   MOVE COURSE idnumber:SOMECOURSE TO runtime:idnumber:NEWCAT
+Using the runtime: special keyword will prevent the parser to evaluate and resolve the identifier, and will store it's initial definition in the handler class. The handler will also NOT try to resolve it at check time, as check time only checks the conditions of execution of all the statements without executing them. At real execution time, the identifier will be resolved to get it's definitive actual value.
+Note that 'runtime' variables may raise a real error situation that cannot be recovered or anticipated by the engine and may terminate in a tecnhical failure of the script and the calling process.
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