[Dbix-class] schema deferred exception documentation patch

[Bob MacCallum]

Hi,

mst helped me solve a little problem (thanks) and he suggested I
contribute a doc patch - I hope this is what he meant.

If you think the patch requires an explanation of *why* you would want
to do this (getting a single list of errors when loading a large chunk
of data is better than going through multiple rounds of fixing errors)
then I can add something to that effect.

cheers,
Bob.


(patch also attached (gmail will probably mangle the long lines))

% diff -ur DBIx-Class-0.08196 DBIx-Class-0.08196-docpatch
diff -ur DBIx-Class-0.08196/lib/DBIx/Class/Schema.pm
DBIx-Class-0.08196-docpatch/lib/DBIx/Class/Schema.pm
--- DBIx-Class-0.08196/lib/DBIx/Class/Schema.pm	2011-11-29
05:15:48.000000000 +0000
+++ DBIx-Class-0.08196-docpatch/lib/DBIx/Class/Schema.pm	2012-05-21
15:32:49.000000000 +0100
@@ -649,6 +649,33 @@

 Connecting with C<< AutoCommit =3D> 1 >> is recommended.

+Using nested calls of txn_do as outlined below, it is possible to
+defer exceptions (e.g. from which a temporary recovery might be
+possible) until the end of the transaction.
+
+  package My::Schema;
+  # ...
+  sub txn_do_deferred {
+    my ($self, $coderef, @args) =3D @_;
+    my $retval;
+    $self->txn_do( sub {
+  		   $self->{deferred_exceptions} =3D [];
+  		   $retval =3D $self->txn_do($coderef, @args);
+  		   if (@{$self->{deferred_exceptions}}) {
+  		     warn "The following deferred exceptions were encountered:\n  ".
+  		       join("\n  ", @{$self->{deferred_exceptions}})."\nRolling back..=
.\n";
+  		     $self->txn_rollback();
+  		   }
+  		 }
+  	       );
+    return $retval;
+  }
+
+  sub defer_exception {
+    my ($self, $msg) =3D @_;
+    push @{$self->{deferred_exceptions}}, $msg;
+  }
+
 =3Dcut

 sub txn_do {
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