Configurability 1.0.2

Version 1.0.2 of configurability has been released.

Configurability is a mixin that allows you to add configurability to one
or
more objects or classes. You can assign them each a subsection of the
configuration, and then later, when the configuration is loaded, the
configuration is split up and sent to the objects that will use it.

Usage

To add configurability to a class, just require the library and extend
the class:

require 'configurability'
class User
    extend Configurability
end

Or, add it to a instance:

user = User.new
user.extend( Configurability )

Later, when you’ve loaded the configuration, can can call

Configurability.configure_objects( config )

and the config will be spliced up and sent to all the objects that
have
been extended with it. Configurability expects the configuration to be
broken up into a number of sections, each of which is accessible via
either
a method with the section name or the index operator (#[]) that
takes the
section name as a Symbol or a String:

config.section_name
config[:section_name]
config['section_name']

The section name is based on an object’s config key, which is the name
of
the object that is being extended with all non-word characters converted
into
underscores (_) by default. It will also have any leading Ruby-style
namespaces stripped, e.g.,

MyClass            -> :myclass
Acme::User         -> :user
"J. Random Hacker" -> :j_random_hacker

If the object responds to the #name method, then the return value of
that
method is used to derive the name. If it doesn’t have a #name method,
the
name of its Class will be used instead. If its class is anonymous,
then
the object’s config key will be :anonymous.

When the configuration is loaded, if you haven’t customized anything, an
instance variable called @config is set to the appropriate section of
the
config object for each object that has been extended with
Configurability.

Customization

The default behavior above is just provided as a reasonable default; it
is
expected that you’ll want to customize at least one or two things about
how configuration is handled in your objects.

Setting a Custom Config Key

The first thing you might want to do is change the config section that
corresponds to your object. You can do that by declaring a different
config key, either using a declarative method:

class OutputFormatter
    extend Configurability
    config_key :format
end

or by overriding the #config_key method and returning the desired
value
as a Symbol:

class User
    extend Configurability
    def self::config_key
        return :employees
    end
end

Changing How an Object Is Configured

You can also change what happens when an object is configured by
implementing
a #configure method that takes the config section as an argument:

class WebServer
    extend Configurability

    config_key :webserver

    def self::configure( configsection )
        @default_bind_addr = configsection[:host]
        @default_port = configsection[:port]
    end
end

If you still want the @config variable to be set, just super from
your
implementation; don’t if you don’t want it to be set.

Configuration Objects

Configurability also includes Configurability::Config, a fairly simple
configuration object class that can be used to load a YAML configuration
file,
and then present both a Hash-like and a Struct-like interface for
reading
configuration sections and values; it’s meant to be used in tandem with
Configurability, but it’s also useful on its own.

Here’s a quick example to demonstrate some of its features. Suppose you
have a
config file that looks like this:

---
database:
  development:
    adapter: sqlite3
    database: db/dev.db
    pool: 5
    timeout: 5000
  testing:
    adapter: sqlite3
    database: db/testing.db
    pool: 2
    timeout: 5000
  production:
    adapter: postgres
    database: fixedassets
    pool: 25
    timeout: 50
ldap:
  uri: ldap://ldap.acme.com/dc=acme,dc=com
  bind_dn: cn=web,dc=acme,dc=com
  bind_pass: [email protected]@ge
branding:
  header: "#333"
  title: "#dedede"
  anchor: "#9fc8d4"

You can load this config like so:

require 'configurability/config'
config = Configurability::Config.load( 'examples/config.yml' )
# => #<Configurability::Config:0x1018a7c7016 loaded from
    examples/config.yml; 3 sections: database, ldap, branding>

And then access it using struct-like methods:

config.database
# => #<Configurability::Config::Struct:101806fb816
    {:development=>{:adapter=>"sqlite3", :database=>"db/dev.db", 

:pool=>5,
:timeout=>5000}, :testing=>{:adapter=>“sqlite3”,
:database=>“db/testing.db”, :pool=>2, :timeout=>5000},
:production=>{:adapter=>“postgres”, :database=>“fixedassets”,
:pool=>25, :timeout=>50}}>

config.database.development.adapter
# => "sqlite3"

config.ldap.uri
# => "ldap://ldap.acme.com/dc=acme,dc=com"

config.branding.title
# => "#dedede"

or using a Hash-like interface using either Symbols, Strings, or a mix
of
both:

config[:branding][:title]
# => "#dedede"

config['branding']['header']
# => "#333"

config['branding'][:anchor]
# => "#9fc8d4"

You can install it via the Configurability interface:

config.install

Check to see if the file it was loaded from has changed since you
loaded it:

config.changed?
# => false

# Simulate changing the file by manually changing its mtime
File.utime( Time.now, Time.now, config.path )
config.changed?
# => true

If it has changed (or even if it hasn’t), you can reload it, which
automatically re-installs it via the Configurability interface:

config.reload

You can make modifications via the same Struct- or Hash-like interfaces:

config.database.testing.adapter = 'mysql'
config[:database]['testing'].database = 't_fixedassets'

then dump it to a YAML string:

config.dump
# => "--- \ndatabase: \n  development: \n    adapter: sqlite3\n
    database: db/dev.db\n    pool: 5\n    timeout: 5000\n  testing: 

\n
adapter: mysql\n database: t_fixedassets\n pool: 2\n
timeout:
5000\n production: \n adapter: postgres\n database:
fixedassets\n pool: 25\n timeout: 50\nldap: \n uri:
ldap://ldap.acme.com/dc=acme,dc=com\n bind_dn:
cn=web,dc=acme,dc=com\n bind_pass: [email protected]@ge\nbranding: \n
header: “#333”\n title: “#dedede”\n anchor: “#9fc8d4”\n"

or write it back to the file it was loaded from:

config.write

Development

You can submit bug reports, suggestions, and read more about future
plans at
the project page:

http://bitbucket.org/ged/configurability

or clone it with Mercurial from the same address.

If you prefer git, it’s also mirrored on Github:

http://github.com/ged/configurability

Changes

1.9.2 fixes and updated the shared behavior for RSpec 2.

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