is_* methods and primary key validation

diff --git a/Changes b/Changes
index e2d3a71..e14e816 100644 (file)
--- a/Changes
+++ b/Changes
@@ -2,6 +2,8 @@
 Revision history for DBIx::Class::Tree
 
 0.01000
+    - Added is_leaf, is_root, and is_branch to AdjacencyList.
+    - Added a validation override for set_primary_key().
     - Removed the _grouping_clause override method.
     - Created a TODO document.
     - attach_child() attach_sibling() now accept more than 

diff --git a/TODO b/TODO
index 0029a96..1e666a1 100644 (file)
--- a/TODO
+++ b/TODO
@@ -1,6 +1,5 @@
 
  - Support DAGs.
- - Add is_leaf, is_parent, is_branch, and is_root.
  - Tree::Visitor
  - Come up with a better name for attach_before and 
    attach_after.

diff --git a/lib/DBIx/Class/Tree.pm b/lib/DBIx/Class/Tree.pm
index 86bc7ce..7ce2535 100644 (file)
--- a/lib/DBIx/Class/Tree.pm
+++ b/lib/DBIx/Class/Tree.pm
@@ -23,9 +23,26 @@ trees of data with DBIx::Class.
 
 =head1 COMPONENTS
 
-L<DBIx::Class::Tree::AdjacencyList> - Manage a tree of data using the common adjacency list model. (EXPERIMENTAL)
-
-L<DBIx::Class::Tree::AdjacencyList::Ordered> - Glue DBIx::Class::Ordered and DBIx::Class::Tree::AdjacencyList together. (EXPERIMENTAL)
+L<DBIx::Class::Tree::AdjacencyList> - Manage a tree of data using the 
+common adjacency list model. (EXPERIMENTAL)
+
+L<DBIx::Class::Tree::AdjacencyList::Ordered> - Glue DBIx::Class::Ordered 
+and DBIx::Class::Tree::AdjacencyList together. (EXPERIMENTAL)
+
+=head1 DAG
+
+All tree related modules must conform to have and use the basic traversal 
+methods of a DAG.  For the most part this just means that Tree modules 
+must provide the appearance of having multiple parents per node (via a 
+parents() method) but may very well never return more than one parent.  
+All utility modules, such as a Visitor module, should do its best to 
+never assume that a node only has one parent.  There are situations 
+where this is not possible - in those cases the module's documentation 
+should clearly state that it is not compatible with DAGs.
+
+So far there is no Tree::DAG module, but there will be.  These requirements 
+are vague, and the requirements of Tree modules to be DAG compatible will 
+become more defined in due course.
 
 =head1 AUTHOR
 

diff --git a/lib/DBIx/Class/Tree/AdjacencyList.pm b/lib/DBIx/Class/Tree/AdjacencyList.pm
index 4c9a758..58c0961 100644 (file)
--- a/lib/DBIx/Class/Tree/AdjacencyList.pm
+++ b/lib/DBIx/Class/Tree/AdjacencyList.pm
@@ -207,6 +207,67 @@ sub attach_sibling {
     return $return;
 }
 
+=head2 is_leaf
+
+  if ($obj->is_leaf()) { ... }
+
+Returns 1 if the object has no children, and 0 otherwise.
+
+=cut
+
+sub is_leaf {
+    my( $self ) = @_;
+    return $self->result_source->resultset->search(
+        { $self->_parent_column => $self->id() },
+        { limit => 1 }
+    )->count();
+}
+
+=head2 is_root
+
+  if ($obj->is_root()) { ... }
+
+Returns 1 if the object has no parent, and 0 otherwise.
+
+=cut
+
+sub is_root {
+    my( $self ) = @_;
+    return ( $self->get_column( $self->_parent_column ) ? 1 : 0 );
+}
+
+=head2 is_branch
+
+  if ($obj->is_branch()) { ... }
+
+Returns 1 if the object has a parent and has children.  
+Returns 0 otherwise.
+
+=cut
+
+sub is_branch {
+    my( $self ) = @_;
+    return ( ($self->is_leaf() or $self->is_root()) ? 0 : 1 );
+}
+
+=head2 set_primary_key
+
+This method is an override of DBIx::Class' method for setting the 
+class' primary key column(s).  This method passes control right on 
+to the normal method after first validating that only one column is 
+being selected as a primary key.  If more than one column is then 
+an error will be thrown.
+
+=cut
+
+sub set_primary_ley {
+    my $self = shift;
+    if (@_>1) {
+        croak('You may only specify a single column as the primary key for adjacency tree classes');
+    }
+    return $self->next::method( @_ );
+}
+
 1;
 __END__