Centroid - Ruby

This document includes information specific to Ruby in Centroid. Refer to the Centroid document for general information, including information the JSON configuration file.

Installation

The Centroid Ruby package is hosted at rubygems.org. Install Centroid using gem with gem install centroid or clone the repo and then gem build centroid.gemspec and gem install -l centroid from the ruby/ directory.

Config Class with Ruby

In Ruby, the Centroid::Config class exposes the following:

  • Static from_file class method
  • Initializer
  • for_environment instance method
  • has_key? instance method

Note: The examples given in the following sections are based on the JSON configuration file examples in the Centroid document.

from_file Class Method

Using the static Centroid::Config.from_file(filename) class method, you can create an instance of Config from a JSON file, as in the example below. 

# from_file.rb
config = Centroid::Config.from_file("config.json")
server = config.database.server_address # => "my-server.local"

Config Initializer

To load a string instead of a file, create an instance of Config by passing a JSON string to the Config initializer, as in the following example.

# from_string.rb
json = '{ "database": { "serverAddress": "my-server.local" } }'
config = Centroid::Config.new(json)
server = config.database.server_address # => "my-server.local"

for_environment Instance Method

In the Config instance, you can use the for_environment instance method to retrieve the configuration values for an environment.

If you specify an environment in for_environment, Centroid will merge the requested environment's configuration values with the values in all. Refer to Examples in the Centroid document for information on creating an environment-based JSON configuration file.

With the following example, Centroid will merge the configuration for prod with the configuration for all; the result is then available from a new instance of Config.

# for_enviroment.rb
config = Centroid::Config.from_file("config.json").for_environment("prod")
server = config.some_resource.server # => "resource-prod.local"
solution_path = config.keys.ssh # => "path/to/id_rsa.pub"

has_key? Instance Method

In a Config instance, you can use the has_key? method to determine if a key exists. has_key? is also aliased as include?. These methods use the same case and underscore rules as is used for value lookups.

json = '{ "database": { "serverAddress": "my-server.local" } }'
config = Centroid::Config.new(json)
config.has_key?(:database) # => true
config.include?("DoesNotExist") # => false