Provided by: libconfig-model-perl_2.117-1_all 
NAME
Config::Model::Backend::Any - Virtual class for other backends
VERSION
version 2.117
SYNOPSIS
package Config::Model::Backend::Foo ;
use Mouse ;
extends 'Config::Model::Backend::Any';
# mandatory
sub read {
my $self = shift ;
my %args = @_ ;
# args are:
# root => './my_test', # fake root directory, used for tests
# config_dir => /etc/foo', # absolute path
# file => 'foo.conf', # file name
# file_path => './my_test/etc/foo/foo.conf'
# io_handle => $io # IO::File object opened for read
# check => yes|no|skip
return 0 unless defined $args{io_handle} ; # or die, your choice
# read the file line by line
# we assume the file contain lines like 'key=value'
foreach ($args{io_handle}->getlines) {
chomp ; # remove trailing \n
s/#.*// ; # remove any comment
next unless /\S/; # skip blank line
# $data is 'foo=bar' which is compatible with load
$self->node->load(steps => $_, check => $args{check} ) ;
}
return 1 ;
}
# mandatory
sub write {
my $self = shift ;
my %args = @_ ;
# args are:
# root => './my_test', # fake root directory, used for tests
# config_dir => /etc/foo', # absolute path
# file => 'foo.conf', # file name
# file_path => './my_test/etc/foo/foo.conf'
# io_handle => $io # IO::File object opened for write
# check => yes|no|skip
my $ioh = $args{io_handle} ;
# read the content of the configuration tree
foreach my $elt ($self->node->children) {
# read the value from element $elt
my $v = $self->node->grab_value($elt) ;
# write value in file
$ioh->print(qq!$elt="$v"\n!) if defined $v ;
}
return 1;
}
DESCRIPTION
Some application have configuration files with a syntax which is not supported by existing
"Config::Model::Backend::*" classes.
In this case a new backend must be written. "Config::Model::Backend::Any" was created to
facilitate this task.
The new backend class must use Mouse and must extends (inherit)
"Config::Model::Backend::Any".
How to write your own backend
Declare the new backend in a node of the model
As explained in "Backend specification" in Config::Model::BackendMgr, the new backend must
be declared as an attribute of a Config::Model::Node specification.
Let's say your new backend is "Config::Model::Backend::Foo". This new backend can be
specified with:
rw_config => {
backend => 'Foo' , # can also be 'foo'
config_dir => '/etc/cfg_dir'
file => 'foo.conf', # optional
}
(The backend class name is constructed with "ucfirst($backend_name)")
"rw_config" can also have custom parameters that are passed verbatim to
"Config::Model::Backend::Foo" methods:
rw_config => {
backend => 'Foo' , # can also be 'foo'
config_dir => '/etc/cfg_dir'
file => 'foo.conf', # optional
my_param => 'my_value',
}
"Config::Model::Backend::Foo" class must inherit (extend) Config::Model::Backend::Any and
is expected to provide the following methods:
read
"read()" is called with the following parameters:
%custom_parameters, # e.g. my_param => 'my_value' in the example above
object => $obj, # Config::Model::Node object
root => $root_dir, # fake root directory, used for tests
backend => $backend, # backend name
config_dir => $read_dir, # path below root
file => 'foo.conf', # file name
file_path => $full_name, # full file name (root+path+file)
io_handle => $io_file # IO::File object opened for read
check => [yes|no|skip]
The IO::File object is undef if the file cannot be read.
This method must return 1 if the read was successful, 0 otherwise.
Following the "my_param" example above, %custom_parameters contains " ( 'my_param' ,
'my_value' ) ", so "read()" is called with "root", "config_dir", "file_path",
"io_handle" and "my_param => 'my_value'".
write
"write()" is called with the following parameters:
%$custom_parameters, # e.g. my_param => 'my_value' in the example above
object => $obj, # Config::Model::Node object
root => $root_dir, # fake root directory, used for tests
auto_create => $auto_create, # boolean specified in backend declaration
auto_delete => $auto_delete, # boolean specified in backend declaration
backend => $backend, # backend name
config_dir => $write_dir, # override from instance
file => 'foo.conf', # file name
file_path => $full_name, # full file name (root+path+file)
io_handle => $fh, # IO::File object
write => 1, # always
check => [ yes|no|skip] ,
backup => [ undef || '' || suffix ] # backup strategy required by user
The IO::File object is undef if the file cannot be written to.
This method must return 1 if the write was successful, 0 otherwise
If "io_handle" is defined, the backup has already been done before opening the config
file. If "io_handle" is not defined, there's not enough information in the model to
read the configuration file and create the backup. Your "write()" method will have to
do the backup requested by user.
When both "config_dir" and "file" are specified, the backend manager opens the
configuration file for write (and thus clobbers it) before calling the "write" call-
back with the file handle with "io_handle" parameter. "write" should use this handle
to write data in the target configuration file.
If this behavior causes problem, the solution is to override "skip_open" method in
your backend to return 1.
How to test your new backend
Using Config::Model::Tester, you can test your model with your backend following the
instructions given in Config::Model::Tester.
You can also test your backend with a minimal model (and Config::Model::Tester). In this
case, you need to specify a small model to test in a "*-test-conf.pl" file. See the
IniFile backend test <https://github.com/dod38fr/config-
model/blob/master/t/model_tests.d/backend-ini-test-conf.pl> for an example and its
examples files <https://github.com/dod38fr/config-
model/tree/master/t/model_tests.d/backend-ini-examples>.
CONSTRUCTOR
new ( node => $node_obj, name => backend_name )
The constructor should be used only by Config::Model::Node.
Methods to override
annotation
Whether the backend supports reading and writing annotation (a.k.a comments). Default is
0. Override this method to return 1 if your backend supports annotations.
read
Read the configuration file. This method must be overridden.
write
Write the configuration file. This method must be overridden.
Methods
node
Return the node (a Config::Model::Node) holding this backend.
instance
Return the instance (a Config::Model::Instance) holding this configuration.
show_message( string )
Show a message to STDOUT (unless overridden). Delegated to "show_message( string )" in
Config::Model::Instance.
read_global_comments
Parameters:
• array ref of string containing the lines to be parsed
• A string to specify how a comment is started. Each character is recognized as a
comment starter (e.g '"#;"' allow a comment to begin with '"#"' or '";"')
Read the global comments (i.e. the first block of comments until the first blank or non
comment line) and store them as root node annotation.
Example:
$self->read_global_comments( \@lines, ';');
$self->read_global_comments( \@lines, '#;');
associates_comments_with_data
Parameters:
• array ref of string containing the lines to be parsed
• A string to specify how a comment is started. Each character is recognized as a
comment starter (e.g '"#;"' allow a comment to begin with '"#"' or '";"')
This method extracts comments from the passed lines and associate them with actual data
found in the file lines. Data is associated with comments preceding or on the same line as
the data. Returns a list of [ data, comment ].
Example:
my @lines = (
'# Foo comments',
'foo= 1',
'Baz = 0 # Baz comments'
);
my @res = $self->associates_comments_with_data( \@lines, '#')
# @res is:
# ( [ 'foo= 1', 'Foo comments' ] , [ 'Baz = 0' , 'Baz comments' ] )
write_global_comments( io_handle , comment_char)
Write global comments from configuration root annotation into the io_handle (if defined).
Returns the string written to the io_handle.
write_data_and_comments( io_handle , comment_char , data1, comment1, data2, comment2 ...)
Write data and comments in the "io_handle" (if defined). Comments are written before the
data. Returns the string written to the io_handle. If a data is undef, the comment is
written on its own line.
Replacing a custom backend
Custom backend are now deprecated and must be replaced with a class inheriting this
module.
Please:
• Rename your class to begin with "Config::Model::Backend::"
• Add "use Mouse ;" and "extends 'Config::Model::Backend::Any';" in the header of your
custom class.
• Add "my $self = shift;" as the beginning of "read" and "write" functions... well...
methods.
Here's an example of such a change <https://github.com/dod38fr/config-
model/commit/c3b7007ad386cb2356c5ac1499fe51bdf492b19a>.
AUTHOR
Dominique Dumont, (ddumont at cpan dot org)
SEE ALSO
Config::Model, Config::Model::BackendMgr, Config::Model::Node,
Config::Model::Backend::Yaml,
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