NAME

Config::Model::ObjTreeScanner - Scan config tree and perform call-backs

SYNOPSIS

 use Config::Model::ObjTreeScanner ;

 # define configuration tree object
 my $root = ... ;

 # define leaf call back
 my disp_leaf = sub { 
      my ($scanner, $data_ref, $node,$element_name,$index, $leaf_object) = @_ ;
      $$data_ref .= "$element_name = ", $leaf_object->fetch ;
    } ;

 # simple scanner, (print all values with 'intermediate' permission
 $scan = Config::Model::ObjTreeScanner-> new
  (
   leaf_cb               => \&disp_leaf, # only mandatory parameter
  ) ;

 my $result = '';

 $scan->scan_node(\$result, $root) ;
 

 # For a more complex scanner

 $scan = Config::Model::ObjTreeScanner-> new
  (
   fallback => 'none',     # all callback must be defined
   permission => 'master', # consider all values

   # node callback
   list_cb       => \&disp_hash    ,
   check_list_cb => \&disp_hash    ,
   hash_cb       => \&disp_hash    ,
   element_cb    => \&disp_obj     ,
   node_cb       => \&disp_obj_elt ,

   # leaf callback
   leaf_cb               => \&disp_leaf,
   enum_value_cb         => \&disp_leaf,
   enum_integer_value_cb => \&disp_leaf,
   integer_value_cb      => \&disp_leaf,
   number_value_cb       => \&disp_leaf,
   boolean_value_cb      => \&disp_leaf,
   string_value_cb       => \&disp_leaf,
   reference_value_cb    => \&disp_leaf,
  ) ;

 $scan->scan_node(\$result, $root) ;

DESCRIPTION

This module creates an object that will explore (depth first) a configuration tree.

For each node or leaf encountered, the ObjTreeScanner object will call-back one of the subroutine reference passed during construction.

To continue the exploration, these call-backs must also call the scanner. (i.e. perform another call-back). In other words the user's subroutine and the scanner plays a game of ping-pong until the tree is completely explored.

The scanner provides a set of default callback for the nodes. This way, the user only have to provide call-backs for the leaves.

The scan is started with a call to scan_node. The first parameter of scan_node is a ref that is passed untouched to all call-back. This ref may be used to store whatever result you want.

CONSTRUCTOR

new ( ... )

One way or another, the ObjTreeScanner object must be able to find all callback for all the items of the tree. All the possible call-back are listed below:

leaf callback:

leaf_cb, enum_value_cb, enum_integer_value_cb, integer_value_cb, number_value_cb, boolean_value_cb, string_value_cb, reference_value_cb

node callback:

list_cb, check_list_cb, hash_cb, element_cb, node_cb.

The user may specify all of them by passing the sub ref to the constructor:

   $scan = Config::Model::ObjTreeScanner-> new
  (
   # node callback
   list_cb => sub ,
   ...
  )

Or use some default callback using the fallback parameter. Note that at least one callback must be provided: leaf_cb.

Optional parameter:

fallback

If set to 'node', the scanner will provide default call-back for node items. If set to 'leaf', the scanner will set all leaf callback (like enum_integer_value_cb, enum_value_cb ...) to string_value_cb or to the mandatory leaf_cb value. "fallback" callback will not override callbacks provided by the user.

If set to 'all', equivalent to 'node' and 'leaf'.

permission

Set the privilege level used for the scan (default 'intermediate').

auto_vivify

Whether to create the configuration items while scan (default is 1).

Callback prototypes

The leaf callback will be called with the following parameters:

 ($scanner, $data_ref,$node,$element_name,$index, $leaf_object) 

where:

• $scanner is the scanner object.

• $data_ref is the reference passwd to the first call of the scanner.

• $node is the node that contain the leaf.

• $element_name is the element (or attribute) that contain the leaf.

• $index is the index (or hash key) used to get the leaf. This may be undefined if the element type is scalar.

• $leaf_object is a Config::Model::Value object.

Others :

list_cb :

 ($scanner, $data_ref,$node,$element_name,@indexes)

@indexes is an list containing all the indexes of the array.

Example:

  sub my_list_cb {
     my ($scanner, $data_ref,$node,$element_name,@idx) = @_ ;

     # custom code using $data_ref

     # resume exploration (if needed)
     map {$scanner->scan_list($data_ref,$node,$element_name,$_)} @idx ;
  }

check_list_cb :

 ($scanner, $data_ref,$node,$element_name,@indexes)

@indexes is an list containing all the indexes of the array.

hash_cb:

 ($scanner, $data_ref,$node,$element_name,@keys)

@keys is an list containing all the keys of the hash.

Example:

  sub my_hash_cb {
     my ($scanner, $data_ref,$node,$element_name,@keys) = @_ ;

     # custom code using $data_ref

     # resume exploration
     map {$scanner->scan_hash($data_ref,$node,$element_name,$_)} @keys ;
  }

element_cb:

 ($scanner, $data_ref,$node,@element_list)

@element_list contains all the elements of the node.

Example:

  sub my_element_cb = { 
     my ($scanner, $data_ref,$node,@element) = @_ ;

     # custom code using $data_ref

     # resume exploration
     map {$scanner->scan_element($data_ref, $node,$_)} @element ;
  }

node_cb

 ($scanner, $data_ref,$node,$element_name,$key, $next_node)

$key may be undef if $node's element not a hash or a list. $element_name and $key specifies the element name and key of the the node you want to scan. (passed with $next_node) Note that $next_node may be undef if auto_vivify is 0.

Example:

  sub my_node_cb {
    my ($scanner, $data_ref,$node,$element_name,$key, $next_node) = @_

    # your custom code using $data_ref

    # explore next node 
    $scanner->scan_node($data_ref,$next_node);
  }

METHODS

scan_node ($data_r,$node)

Explore the node and call element_cb passing all element names.

scan_element($data_r,$node,$element_name)

Explore the element and call either hash_cb, list_cb, node_cb or a leaf call-back (the leaf call-back called depends on the Value object properties: enum, string, integer and so on)

scan_hash ($data_r,$node,$element_name,$key)

Explore the hash member (or hash value) and call either node_cb or a leaf call-back.

scan_list ($data_r,$node,$element_name,$index)

Just like scan_hash: Explore the list member and call either node_cb or a leaf call-back.

get_keys ($node, $element_name)

Returns an list containing the sorted keys of a hash element or returns an list containning (0.. last_index) of an list element.

Throws an exception if element is not an list or a hash element.

SEE ALSO

Config::Model::Value

cpanm Config::Model

perl -MCPAN -e shell
install Config::Model