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Load configuration settings from ENV, dotfiles, and gems
Ruby
tag: v0.0.2

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README.md

Constellation

Constellation is a powerful configuration system. It's great for API client libraries and applications and anywhere else you need to let your users set some configuration parameters.

Usage

Ruby Parameters

Start by creating a class and calling acts_as_constellation

class MyConfiguration
  acts_as_constellation
end

With just this, you have a basic Hash configuration. The only way to set properties is to pass them in Ruby:

config = MyConfiguration.new(:foo => 'bar')
...
config.foo # => "bar"

ENV

To add support for ENV hash configuration, set env_params:

class MyConfiguration
  self.env_params = { :foo => 'MY_FOO' }
end

...
ENV['MY_FOO'] = 'bar'
...
config = MyConfiguration.new
config.foo # => "bar"

### Configuration Files

To add support for config files, set `config_file` to a path. The Constellation
will look up a config file in that location relative to two places ("base paths"):

 * the current working directory (`Dir.pwd`)
 * the user's home directory (`ENV['HOME']`)

```ruby
class MyConfiguration
  self.config_file = 'my/config.yml'
end

If ./my/config.yml contains the following

--- 
foo: bar

then MyConfiguration.new.foo will return "bar".

From Gems

If you set config_file to a path and set load_from_gems to true, then Constellation will add all of the loaded gem directories to the list of base paths.

class MyConfiguration
  self.config_file = 'my/config.yml'
  self.load_from_gems = true
end

Order of Precedence

Constellation will load parameters in the order listed above. Given

class MyConfiguration
  self.env_params = { :foo => 'MY_FOO' }
  self.config_file = 'my/config.yml'
  self.load_from_gems = true
end

Constellation will first look in a Hash passed in, then in ENV, then in ./my/config.yml, then in ~/my/config.yml, then in GEM_PATH/my/config.yml for each loaded gem.

File Parsers

Constellation will do the right thing if config_file ends with .yml, .yaml, or .json. If it's a different format, you'll have to tell Constellation how to parse it by redefining parse_config_file:

class MyConfiguration
  self.config_file = '.myrc'

  def parse_config_file(contents)
    result = {}
    contents.split("\n").each do |line|
      k, v = line.split(/:\s*/)
      result[k] = v
    end
    result
  end
end
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