NAME

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

VERSION

       version 2.117

SYNOPSIS

        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
        baz:
          en: hello
          fr: bonjour
          hr: dobar dan
        foo: yada

DESCRIPTION

       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.

       Note:

       •   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

backend parameter

   yaml_class
       By default, this module uses YAML::Tiny. This module has the advantage of being light and
       secure <https://github.com/ingydotnet/yaml-libyaml-pm/issues/45>.  No Perl object can be
       created with YAML tags so YAML::Tiny can be used with YAML files coming from unutrusted
       sources.

       On the other hand, YAML::Tiny does not support boolean values: it cannot write "true" and
       "false" as plain scalar. "true" and "false" are quoted and are not of type boolean from
       YAML point of view.

       If this is a problem for your configuration files, you can use YAML module which writes
       "true" and "false" without quotes.

CONSTRUCTOR

   new ( node => $node_obj, name => 'yaml' ) ;
       Inherited from Config::Model::Backend::Any. The constructor is called by
       Config::Model::BackendMgr.

   read ( io_handle => ... )
       Of all parameters passed to this read call-back, only "io_handle" is used. This parameter
       must be IO::File object already opened for read.

       It can also be undef. In which case "read()" returns 0.

       When a file is read,  "read()" returns 1.

   write ( io_handle => ... )
       Of all parameters passed to this write call-back, only "io_handle" is used. This parameter
       must be IO::File object already opened for write.

       "write()" returns 1.

AUTHOR

       Dominique Dumont, (ddumont at cpan dot org)

SEE ALSO

       Config::Model, Config::Model::BackendMgr, Config::Model::Backend::Any,

AUTHOR

       Dominique Dumont

COPYRIGHT AND LICENSE

       This software is Copyright (c) 2005-2018 by Dominique Dumont.

       This is free software, licensed under:

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