# NAME

Config::Onion - Layered configuration, because configs are like ogres

# VERSION

version 1.000

# SYNOPSIS

    my $cfg = Config::Onion->new;
    my $cfg = Config::Onion->set_default(db => {name => 'foo', password => 'bar'});
    my $cfg = Config::Onion->load('/etc/myapp', './myapp');
    my $cfg = Config::Onion->load_glob('./plugins/*');

    $cfg->set_default(font => 'Comic Sans');
    $cfg->load('config');
    $cfg->load_glob('conf.d/myapp*');
    $cfg->set_override(font => 'Arial');

    my $dbname = $cfg->get->{db}{name};
    my $plain_hashref_conf = $cfg->get;
    my $dbpassword = $plain_hashref_conf->{db}{password};

# DESCRIPTION

All too often, configuration is not a universal or one-time thing, yet most
configuration-handling treats it as such.  Perhaps you can only load one config
file.  If you can load more than one, you often have to load all of them at the
same time or each is stored completely independently, preventing one from being
able to override another.  Config::Onion changes that.

Config::Onion stores all configuration settings in four layers: Defaults,
Main, Local, and Override.  Each layer can be added to as many times as you
like.  Within each layer, settings which are given multiple times will take the
last specified value, while those which are not repeated will remain untouched.

    $cfg->set_default(name => 'Arthur Dent', location => 'Earth');
    $cfg->set_default(location => 'Magrathea');
    # In the Default layer, 'name' is still 'Arthur Dent', but 'location' has
    # been changed to 'Magrathea'.

Regardless of the order in which they are set, values in Main will always
override values in the Default layer, the Local layer always overrides both
Default and Main, and the Override layer overrides all the others.

The design intent for each layer is:

- Default

    Hardcoded default values to be used when no further configuration is present

- Main

    Values loaded from standard configuration files shipped with the application

- Local

    Values loaded from local configuration files which are kept separate to prevent
    them from being overwritten by application upgrades, etc.

- Override

    Settings provided at run-time which take precendence over all configuration
    files, such as settings provided via command line switches

    # METHODS

    ## new

    Returns a new, empty configuration object.

    ## load(@file\_stems)

    Loads files matching the given stems using `Config::Any->load_stems` into
    the Main layer.  Also concatenates ".local" to each stem and loads matching
    files into the Local layer.  e.g., `$cfg->load('myapp')` would load
    `myapp.yml` into Main and `myapp.local.js` into Local.  All filename
    extensions supported by `Config::Any` are recognized along with their
    corresponding formats.

    ## load\_glob(@globs)

    Uses the Perl `glob` function to expand each parameter into a list of
    filenames and loads each file using `Config::Any`.  Files whose names contain
    the string ".local." are loaded into the Local layer.  All other files are
    loaded into the Main layer.

    ## set\_default(\[\\%settings,...,\] %settings)

    ## set\_override(\[\\%settings,...,\] %settings)

    Imports `%settings` into the Default or Override layer.  Accepts settings both
    as a plain hash and as hash references, but, if the two are mixed, all hash
    references must appear at the beginning of the parameter list, before any
    non-hashref settings.

    # PROPERTIES

    ## cfg

    ## get

    Returns the complete configuration as a hash reference.

    ## default

    ## main

    ## local

    ## override

    These properties each return a single layer of the configuration.  This is
    not likely to be useful other than for debugging.  For most other purposes,
    you probably want to use `get` instead.

    # BUGS AND LIMITATIONS

    No bugs have been reported.

    Please report any bugs or feature requests at
    [https://github.com/dsheroh/Config-Onion/issues](https://github.com/dsheroh/Config-Onion/issues)

    # AUTHOR

    Dave Sherohman <dsheroh@cpan.org>

    # COPYRIGHT AND LICENSE

    This software is copyright (c) 2013 by Lund University Library.

    This is free software; you can redistribute it and/or modify it under
    the same terms as the Perl 5 programming language system itself.
