--- name: "Config::Model::Backend::Any" section: "3pm" platform: "linux" package: "libconfig-model-perl" version: "2.155-1" release: "Debian 13 (Trixie)" platforms: ["linux"] url: "https://new.carta.tech/Config::Model::Backend::Any" --- # Config::Model::Backend::Any(3pm) Virtual class for other backends ## NAME Config::Model::Backend::Any - Virtual class for other backends ## VERSION version 2.155 ## 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 => Path::Tiny object for './my_test/etc/foo/foo.conf' # check => yes|no|skip return 0 unless $args{file_path}->exists ; # or die, your choice # read the file line by line # we assume the file contain lines like 'key=value' foreach ($args{file_path}->lines_utf8) { 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 => Path::Tiny object for './my_test/etc/foo/foo.conf' # check => yes|no|skip # read the content of the configuration tree my @lines; foreach my $elt ($self->node->children) { # read the value from element $elt my $v = $self->node->grab_value($elt) ; # write value in file push @lines,qq!$elt="$v"\n! if defined $v ; } $args{file_path}->spew_utf8(@lines); return 1; } ``` ## DESCRIPTION Some application have configuration files with a syntax which is not supported by existing `"Config::Model::Backend::*"` classes. In this case a new backend must be written. `"Config::Model::Backend::Any"` was created to facilitate this task. The new backend class must use Mouse and must extends (inherit) `"Config::Model::Backend::Any"`. ## How to write your own backend ### Declare the new backend in a node of the model As explained in "Backend specification" in Config::Model::BackendMgr, the new backend must be declared as an attribute of a Config::Model::Node specification. Let's say your new backend is `"Config::Model::Backend::Foo"`. This new backend can be specified with: ``` rw_config => { backend => 'Foo' , # can also be 'foo' config_dir => '/etc/cfg_dir' file => 'foo.conf', # optional } ``` (The backend class name is constructed with `ucfirst($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 => $full_name, # Path::Tiny object check => [yes|no|skip] ``` The IO::File object is undef if the file cannot be read. This method must return 1 if the read was successful, 0 otherwise. Following the `"my_param"` example above, `%custom_parameters` contains `" ( 'my_param' , 'my_value' ) "`, so `read()` is called with `"root"`, `"config_dir"`, `"file_path"` **and** `"my_param => 'my_value'"`. - write `"write"` is called with the following parameters: ``` %$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) 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 ### 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 \ for an example and its examples files \. ## CONSTRUCTOR ### new The constructor should be used only by Config::Model::Node. Parameter: - node Calling node object. Node ref is weakened, - name Backend name - auto\_create Boolean. Set to true to create the configuration file if this one is missing (default 0) - auto\_delete Boolean. Set to true to remove the configuration file if this one no longer contain configuration information. (default 0) ## 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 Parameters: `"( string )"` Show a message to STDOUT (unless overridden). Delegated to "show\_message" 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. Note that the global comment must be separated from the first data line by a blank line. 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 Return a string containing global comments using data from configuration root annotation. Requires one parameter: comment\_char (e.g "#" or '//' ) Example: ``` my $str = $self->write_global_comments('#') ``` ### write\_data\_and\_comments Returns a string containing comments (stored in annotation) and corresponding data. Comments are written before the data. If a data is undef, the comment is written on its own line. Positional parameters are `"( comment_char , data1, comment1, data2, comment2 ...)"` Example: ``` print $self->write_data_and_comments('#', 'foo', 'foo comment', undef, 'lone comment','bar') # returns "# foo comment\nfoo\n#lon ``` Use `"undef"` as comment char if comments are not supported by the syntax of the configuration file. Comments will then be dropped. ## 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 \. ## AUTHOR Dominique Dumont, (ddumont at cpan dot org) ## SEE ALSO Config::Model, Config::Model::BackendMgr, Config::Model::Node, ## AUTHOR Dominique Dumont ## COPYRIGHT AND LICENSE This software is Copyright (c) 2005-2022 by Dominique Dumont. This is free software, licensed under: ``` The GNU Lesser General Public License, Version 2.1, February 1999 ```