/ 
Config-Model-2.144
River stage two • 11 direct dependents • 11 total dependents
/ Config::Model::ObjTreeScanner

NAME

Config::Model::ObjTreeScanner - Scan config tree and perform call-backs for each element or node

VERSION

version 2.144

SYNOPSIS

 use Config::Model ;

 # define configuration tree object
 my $model = Config::Model->new ;
 $model ->create_config_class (
    name => "MyClass",
    element => [
        [qw/foo bar/] => {
            type => 'leaf',
            value_type => 'string'
        },
        baz => {
            type => 'hash',
            index_type => 'string' ,
            cargo => {
                type => 'leaf',
                value_type => 'string',
            },
        },

    ],
 ) ;

 my $inst = $model->instance(root_class_name => 'MyClass' );

 my $root = $inst->config_root ;

 # put some data in config tree the hard way
 $root->fetch_element('foo')->store('yada') ;
 $root->fetch_element('bar')->store('bla bla') ;
 $root->fetch_element('baz')->fetch_with_id('en')->store('hello') ;

 # put more data the easy way
 my $steps = 'baz:fr=bonjour baz:hr="dobar dan"';
 $root->load( steps => $steps ) ;

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

 # simple scanner, (print all values)
 my $scan = Config::Model::ObjTreeScanner-> new (
   leaf_cb => $disp_leaf, # only mandatory parameter
 ) ;

 my $result = '';
 $scan->scan_node(\$result, $root) ;
 print $result ;

DESCRIPTION

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

For each part of the configuration tree, ObjTreeScanner object calls one of the subroutine reference passed during construction. (a call-back or a hook)

Call-back and hook routines are called:

  • For each node containing elements (including root node)

  • For each element of a node. This element can be a list, hash, node or leaf element.

  • For each item contained in a node, hash or list. This item can be a leaf or another node.

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 play a game of ping-pong until the tree is completely explored.

Hooks routines are not required to resume the exploration, i.e. to call the scanner. This is done once the hook routine has returned.

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 and hooks are listed below:

leaf callback:

leaf_cb is a catch-all generic callback. All other are specialized call-back : enum_value_cb, integer_value_cb, number_value_cb, boolean_value_cb, string_value_cb, uniline_value_cb, reference_value_cb

node callback:

node_content_cb , node_dispatch_cb

node hooks:

node_content_hook

element callback:

All these call-backs are called on the elements of a node: list_element_cb, check_list_element_cb, hash_element_cb, node_element_cb, node_content_cb.

element hooks:

list_element_hook, hash_element_hook.

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

 $scan = Config::Model::ObjTreeScanner-> new
(
 list_element_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 provides default call-back for node items. If set to leaf, the scanner sets all leaf callback (like enum_value_cb ...) to string_value_cb or to the mandatory leaf_cb value. "fallback" callback does not override callbacks provided by the user.

If set to all , the scanner provides fallbacks for leaf and node. By default, all fallback are provided.

auto_vivify

Whether to create configuration objects while scanning (default is 1).

check

yes, no or skip.

Callback prototypes

Leaf callback

leaf_cb is called for each leaf of the tree. The leaf callback is called with the following parameters:

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

where:

  • $scanner is the scanner object.

  • $data_ref is a reference that is first passed to the first call of the scanner. Then $data_ref is relayed through the various call-backs

  • $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.

List element callback

list_element_cb is called on all list element of a node, i.e. call on the list object itself and not in the elements contained in the list.

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

@indexes is a list containing all the indexes of the list.

Example:

sub my_list_element_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 ;

   # note: scan_list and scan_hash are equivalent
}

List element hook

list_element_hook: Works like the list element callback. Except that the calls to scan_list are not required. This is done once the hook returns.

Check list element callback

check_list_element_cb: Like list_element_cb, but called on a check_list element.

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

index is always undef as a check_list cannot be contained in a hash or list (yet)

Hash element callback

hash_element_cb: Like list_element_cb, but called on a hash element.

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

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

Example:

sub my_hash_element_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 ;
}

Hash element hook

hash_element_hook: Works like the hash element callback. Except that the calls to scan_hash are not required. This is done once the hook returns.

Node content callback

node_content_cb: This call-back is called foreach node (including root node).

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

@element_list contains all the element names of the node.

Example:

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

   # custom code using $data_ref

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

Node content hook

node_content_hook: This hook is called foreach node (including root node). Works like the node content call-back. Except that the calls to scan_element are not required. This is done once the hook returns.

Dispatch node callback

node_dispatch_cb: Any callback specified in the hash is called for each instance of the specified configuration class. (this may include the root node).

For instance, if you have:

node_dispach_cb => {
  ClassA => \&my_class_a_dispatch_cb,
  ClassB => \&my_class_b_dispatch_cb,
}

&my_class_a_dispatch_cb is called for each instance of ClassA and &my_class_b_dispatch_cb is called for each instance of ClassB.

They is called with the following parameters:

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

@element_list contains all the element names of the node.

Example:

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

   # custom code using $data_ref

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

Node element callback

node_element_cb is called for each node contained within a node (i.e not with root node). This node can be held by a plain element or a hash element or a list element:

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

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

Example:

sub my_node_element_cb {
  my ($scanner, $data_ref,$node,$element_name,$key, $contained_node) = @_;

  # your custom code using $data_ref

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

METHODS

scan_node

Parameters: ($data_r,$node)

Explore the node and call either node_dispatch_cb (if the node class name matches the dispatch_node hash) or (e.g. xor) node_element_cb passing all element names.

up_cb is called once the first callback returns.

scan_element

Parameters: ($data_r,$node,$element_name)

Explore the element and call either hash_element_cb, list_element_cb, node_content_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

Parameters: ($data_r,$node,$element_name,$key)

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

scan_list

Parameters: ($data_r,$node,$element_name,$index)

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

get_keys

Parameters: ($node, $element_name)

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

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

AUTHOR

Dominique Dumont, (ddumont at cpan dot org)

SEE ALSO

Config::Model,Config::Model::Node,Config::Model::Instance, Config::Model::HashId, Config::Model::ListId, Config::Model::CheckList, Config::Model::Value

AUTHOR

Dominique Dumont

COPYRIGHT AND LICENSE

This software is Copyright (c) 2005-2021 by Dominique Dumont.

This is free software, licensed under:

The GNU Lesser General Public License, Version 2.1, February 1999