===== MoodleScript: FREEZE CONTEXT =====
===== MoodleScript Script Engine =====

STATUS: Draft.

=== Effect ===

Freezes the execution stack context and prevents the execution of instructions from modifying it.

A number of instructions can alter the value of context variables when they execute. For example, creating a course category sets, by default, the current course category to the newly created category. A succession of category creations using the 'current' meta will create a succession of nested categories.

   ADD CATEGORY My Root TO id:1

   ADD CATEGORY Cat 1 TO current
   
   ADD CATEGORY Cat 2 TO current

   ADD CATEGORY Cat 3 TO current

Will give the following tree:

   Miscelaneous > My Root > Cat 1 > Cat 2 > Cat 3

To successively create "siblings" of the same category, the context must be frozen so that current always represents the initial category before the first addition. Thus:

   ADD CATEGORY My Root TO id:1
   
   FREEZE CONTEXT
   
   ADD CATEGORY Cat 1 TO current
   
   ADD CATEGORY Cat 2 TO current
   
   ADD CATEGORY Cat 3 TO current
   
   UNFREEZE CONTEXT

Will generate a tree like this:

   * Miscelaneous
     * My root
       * Cat 1
       * Cat 2
       * Cat 3

=== Syntax ===

    FREEZE CONTEXT

=== Specific attributes ===

None


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