Config::Model::Backend::Yaml - Read and write config as a YAML data structure


version 2.133


 use Config::Model ;
 use Data::Dumper ;

 # 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',
  rw_config  => {
    backend => 'yaml',
    config_dir => '/tmp',
    file  => 'foo.yml',
    auto_create => 1,
 ) ;

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

 my $root = $inst->config_root ;

 my $steps = 'foo=yada bar="bla bla" baz:en=hello
             baz:fr=bonjour baz:hr="dobar dan"';
 $root->load( steps => $steps ) ;
 $inst->write_back ;

Now, /tmp/foo.yml contains:

 bar: bla bla
   en: hello
   fr: bonjour
   hr: dobar dan
 foo: yada


This module is used directly by Config::Model to read or write the content of a configuration tree written with YAML syntax in Config::Model configuration tree.


  • Undefined values are skipped for list element. I.e. if a list element contains ('a',undef,'b'), the data structure contains 'a','b'.

  • YAML file is not created (and may be deleted) when no data is to be written.

Class with only one hash element

If the root node contains a single hash or list element, only the content of this hash is written in a YAML file.

For example, if a class contains:

      element => [
        baz => {
            type => 'hash',
            index_type => 'string' ,
            cargo => {
                type => 'leaf',
                value_type => 'string',

If the configuration is loaded with:

 $root->load("baz:one=un baz:two=deux")

Then the written YAML file does not show baz:

 one: un
 two: deux

Likewise, a YAML file for a class with a single list baz element would be written with:

 - un
 - deux

YAML class

As of v2.129, this backend uses YAML::XS 0.69 or later.

For security reason, loading a Perl blessed object is disabled.

Value of type boolean are written as boolean values in YAML files.

backend parameter


This parameter is ignored as of version 2.129.



Parameters: ( node => $node_obj, name => 'yaml' )

Inherited from Config::Model::Backend::Any. The constructor is called by Config::Model::BackendMgr.


Read YAML file and load into $node_obj tree.

When a file is read, read returns 1.


Write YAML File using $node_obj data.

write returns 1.


Dominique Dumont, (ddumont at cpan dot org)


Config::Model, Config::Model::BackendMgr, Config::Model::Backend::Any, YAML::XS


Dominique Dumont


This software is Copyright (c) 2018 by Dominique Dumont.

This is free software, licensed under:

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



The following websites have more information about this module, and may be of help to you. As always, in addition to those websites please use your favorite search engine to discover more resources.

Bugs / Feature Requests

Please report any bugs or feature requests by email to ddumont at, or through the web interface at You will be automatically notified of any progress on the request by the system.

Source Code

The code is open to the world, and available for you to hack on. Please feel free to browse it and play with it, or whatever. If you want to contribute patches, please send me a diff or prod me to pull from your repository :)

  git clone git://