NAME

       UR::Context::Transaction - API for software transactions

SYNOPSIS

         my $o = Some::Obj->create(foo => 1);
         print "o's foo is ",$o->foo,"\n";  # prints 1

         my $t = UR::Context::Transaction->begin();

         $o->foo(4);

         print "In transaction, o's foo is ",$o->foo,"\n";  # prints 4

         if (&should_we_commit()) {
             $t->commit();
             print "Transaction committed, o's foo is ",$o->foo,"\n";  # prints 4

         } else {
             $t->rollback();
             print "Transaction rollback, o's foo is ",$o->foo,"\n";  # prints 1
         }

DESCRIPTION

       UR::Context::Transaction instances represent in-memory transactions as a diff of the
       contents of the object cache in the Process context.  Transactions are nestable.  Their
       instances exist in the object cache and  are subject to the same scoping rules as other
       UR-based objects, meaning that they do not disappear mearly because the lexical variable
       they're assigned to goes out of scope.  They must be explicitly disposed of via the commit
       or rollback methods.

INHERITANCE

       UR::Context::Transaction is a subclass of UR::Context

CONSTRUCTOR

       begin
             $t = UR::Context::Transaction->begin();

           Creates a new software transaction context to track changes to UR-based objects.  As
           all activity to objects occurs in some kind of transaction context, the newly created
           transaction exists within whatever context was current before the call to begin().

METHODS

       commit
             $t->commit();

           Causes all objects with changes to save those changes back to the underlying context.

       rollback
             $t->rollback();

           Causes all objects with changes to have those changes reverted to their state when the
           transaction began.  Classes with properties whose meta-property is_transactional => 0
           are not tracked within a transaction and will not be reverted.

       delete
             $t->delete();

           delete() is a synomym for rollback

       has_changes
             $bool = $t->has_changes();

           Returns true if any UR-based objects have changes within the transaction.

       get_changes
             @changes = $t->get_changes();

           Return a list or UR::Change objects representing changes within the transaction.

CLASS METHODS

       execute
             $retval = UR::Context::Transaction->execute($coderef);

           Executes the coderef with no arguments, within an eval and a software transaction.  If
           the coderef returns true, the transaction is committed.  If it returns false, the
           transaction is rolled back.  Finally the coderef's return value is returned to the
           caller.

           If the coderef throws an exception, it will be caught, the transaction rolled back,
           and the exception will be re-thrown with die().

       execute_and_rollback
             UR::Context::Transaction->execute_and_rollback($coderef);

           Executes the coderef with no arguments, within an eval and a software transaction.
           Reguardless of the return value of the coderef, the transaction will be rolled back.

           If the coderef throws an exception, it will be caught, the transaction rolled back,
           and the exception will be re-thrown with die().

SEE ALSO

       UR::Context