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TTY::Config Gitter

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Define, read and write any Ruby app configurations with a penchant for terminal clients.

TTY::Config provides app configuration component for TTY toolkit.

Features

  • Read & write configurations in YAML, JSON, TOML, INI formats
  • Simple interface for adding and reading settings for deeply nested keys
  • Indifferent access for reading settings
  • Merging of configuration settings from other hashes
  • Reading values from environment variables

Installation

Add this line to your application's Gemfile:

gem 'tty-config'

And then execute:

$ bundle

Or install it yourself as:

$ gem install tty-config

Contents

1. Usage

Initialize the configuration and provide the name:

config = TTY::Config.new
config.filename = 'investments'

then configure values for different nested keys with set and append:

config.set(:settings, :base, value: 'USD')
config.set(:settings, :color, value: true)
config.set(:coins, value: ['BTC'])

config.append('ETH', 'TRX', 'DASH', to: :coins)

get any value by using fetch:

config.fetch(:settings, :base)
# => 'USD'

config.fetch(:coins)
# => ['BTC', 'ETH', 'TRX', 'DASH']

and write configration out to investments.yml:

config.write
# =>
# ---
# settings:
#   base: USD
#   color: true
# coins:
#  - BTC
#  - ETH
#  - TRX
#  - DASH

and then to read an investments.yml file, you need to provide the locations to search in:

config.append_path Dir.pwd
config.append_path Dir.home

Finally, read in configuration back again:

config.read

1.1 app

An example of an application configuration:

class App
  attr_reader :config

  def initialize
    @config = TTY::Config.new
    @config.filename = 'investments'
    @config.extname = '.toml'
    @config.append_path Dir.pwd
    @config.append_path Dir.home
  end

  def self.config
    @config ||= self.class.new.config
  end
end

2. Interface

2.1 set

To set configuration setting use set method. It accepts any number of keys and value by either using :value keyword argument or passing a block:

config.set(:base, value: 'USD')
config.set(:base) { 'USD' }

The block version of specifying a value will mean that the value is evaluated every time its being read.

You can also specify deeply nested configuration settings by passing sequence of keys:

config.set :settings, :base, value: 'USD'

is equivalent to:

config.set 'settings.base', value: 'USD'

Internally all configuration settings are stored as string keys for ease of working with configuration files and command line application's inputs.

2.2 set_if_empty

To set a configuration setting only if it hasn't been set before use set_if_empty:

config.set_if_empty :base, value: 'USD'

Similar to set it allows you to specify arbitrary sequence of keys followed by a key value or block:

config.set_if_empty :settings, :base, value: 'USD'

2.3 set_from_env

To read configuration options from environment variables use set_from_env. At minimum it requires a single argument which will match the name of ENV variable. The name of this parameter is case insensitive.

Given the following environment variables:

ENV['HOST'] = '192.168.1.17'
ENV['PORT'] = '7727'

You can make the config aware of the above env variables:

config.set_from_env(:host)
config.set_from_env(:port)

Then you can retrieve values like any other configuration option:

config.fetch(:host)
# => '192.168.1.17'
config.fetch(:port)
# => '7727'

If you want the configuration key name to be different from ENV variable name use a block:

config.set_from_env(:host) { 'HOSTNAME' }
config.set_from_env(:host) { :hostname }

You can also configure settings for deeply nested keys:

config.set_from_env(:settings, :base) { 'CURRENCY' }
config.set_from_env(:settings, :base) { :currency }
config.set_from_env('settings.base') { 'CURRENCY'}
config.set_from_env('settings.base') { :currency}

And asssuming ENV['CURRENCY']=USD:

config.fetch(:settings, :base)
# => USD

You can also prefix your environment variables. See env_prefix=

It's important to recognise that set_from_env doesn't record the value for the environment variables. They are read each time from the ENV when fetch is called.

2.4 fetch

To get a configuration setting use fetch, which can accept default value either with a :default keyword or a block that will be lazy evaluated:

config.fetch(:base, default: 'USD')
config.fetch(:base) { 'USD' }

Similar to set operation, fetch allows you to retrieve deeply nested values:

config.fetch(:settings, :base) # => USD

is equivalent to:

config.fetch('settings.base')

fetch has indifferent access so you can mix string and symbol keys, all the following examples retrieve the value:

config.fetch(:settings, :base)
config.fetch('settings', 'base')
config.fetch(:settings', 'base')
config.fetch('settings', :base)

2.5 merge

To merge in other configuration settings as hash use merge:

config.set(:a, :b, value: 1)
config.set(:a, :c, value: 2)

config.merge({'a' => {'c' => 3, 'd' => 4}})

config.fetch(:a, :c) # => 3
config.fetch(:a, :d) # => 4

Internally all configuration settings are stored as string keys for ease of working with file values and command line applications inputs.

2.6 coerce

You can initialize configuration based on a hash, with all the keys converted to symbols:

hash = {"settings" => {"base" => "USD", "exchange" => "CCCAGG"}}
config = TTY::Config.coerce(hash)
config.to_h
# =>
# {settings: {base: "USD", exchange: "CCCAGG"}}

2.7 append

To append arbitrary number of values to a value under a given key use append:

config.set(:coins) { ["BTC"] }

config.append("ETH", "TRX", to: :coins)
# =>
# {coins: ["BTC", "ETH", "TRX"]}

You can also append values to deeply nested keys:

config.set(:settings, :bases, value: ["USD"])

config.append("EUR", "GBP", to: [:settings, :bases])
# =>
# {settings: {bases: ["USD", "EUR", "GBP"]}}

2.8 remove

Use remove to remove a set of values from a key.

config.set(:coins, value: ["BTC", "TRX", "ETH", "DASH"])

config.remove("TRX", "DASH", from: :coins)
# =>
# ["BTC", "ETH"]

If the key is nested the :from accepts an array:

config.set(:holdings, :coins, value: ["BTC", "TRX", "ETH", "DASH"])

config.remove("TRX", "DASH", from: [:holdings, :coins])
# =>
# ["BTC", "ETH"]

2.9 delete

To completely delete a value and corresponding key use delete:

config.set(:base, value: "USD")
config.delete(:base)
# =>
# "USD"

You can also delete deeply nested keys and their values:

config.set(:settings, :base, value: "USD")
config.delete(:settings, :base)
# =>
# "USD"

2.10 alias_setting

In order to alias a configuration setting to another name use alias_setting.

For example, given an already existing setting:

config.set(:base, value: 'baz')

You can alias it to another name:

config.alias_setting(:base, to: :currency)

And then access like any other configuration setting:

config.fetch(:currency)
# => 'USD'

Deep nested configuration options are also supported:

config.set(:settings, :base, value: 'USD')

And then can be aliased like so:

config.alias_setting(:settings, :base, to: [:settings, :currency])
config.alias_setting('settings.base', to [:settings, :currency])

You can then access the deep nested settings:

config.fetch(:settings, :currency)
# => 'USD'
config.fetch('settings.currency')
# => 'USD'

2.11 validate

To ensure consistency of the data, you can validate values being set at arbitrarily deep keys using validate method, that takes an arbitrarily nested key as its argument and a validation block.

config.validate(:settings, :base) do |key, value|
  if value.length != 3
    raise TTY::Config::ValidationError, "Currency code needs to be 3 chars long."
  end
end

You can assign multiple validations for a given key and each of them will be run in the order they were registered when checking a value.

When setting value all the validaitons will be run:

config.set(:settings, :base, value: 'PL')
# raises TTY::Config::ValidationError, 'Currency code needs to be 3 chars long.'

If the value s provided as a proc or a block then the validation will be delayed until the value is actually read:

config.set(:settings, :base) { 'PL' }
config.fetch(:settings, :base)
# raises TTY::Config::ValidationError, 'Currency code needs to be 3 chars long.'

2.12 env_prefix=

Given the following variables:

ENV['MYTOOL_HOST'] = '192.168.1.17'
ENV['MYTOOL_PORT'] = ' 7727'

You can inform configuration about common prefix using env_prefix:

config.env_prefix = 'mytool'

Then set configuration key name to environment variable name:

config.set_from_env(:host)
config.set_from_env(:port)

And finally retrieve the value:

config.fetch(:host) 
#=> '192.168.1.17'
config.fetch(:port)
# => '7727'

2.13 filename=

By default, TTY::Config searches for config named configuration file. To change this use filename= method without the extension name:

config.filename = 'investments'

Then any supported extensions will be search for such as .yml, .json and .toml.

2.14 extname=

By default '.yml' extension is used to write configuration out to a file but you can change that with extname=:

config.extname = '.toml'

2.15 append_path

You need to tell the TTY::Config where to search for configuration files. To search multiple paths for a configuration file use append_path or prepend_path methods.

For example, if you want to search through /etc directory first, then user home directory and then current directory do:

config.append_path("/etc/")   # look in /etc directory
config.append_path(Dir.home)  # look in user's home directory
config.append_path(Dir.pwd)   # look in current working directory

None of these paths are required, but you should provide at least one path if you wish to read configuration file.

2.16 prepend_path

The prepend_path allows you to add configuration search paths that should be searched first.

config.append_path(Dir.pwd)   # look in current working directory second
config.prepend_path(Dir.home) # look in user's home directory first

2.17 read

There are two ways for reading configuration files and both use the read method. One attempts to guess extension and format of your data, the other allows you to request specific extension and format.

Currently the supported file formats are:

  • yaml for .yaml, .yml extensions
  • json for .json extension
  • toml for .toml extension
  • ini for .ini, .cnf, .conf, .cfg, .cf extensions

Calling read without any arguments searches through provided locations to find configuration file and reads it. Therefore, you need to specify at least one search path that contains the configuration file together with actual filename. When filename is specifed then all known extensions will be tried.

For example, to find file called investments in the current directory do:

config.append_path(Dir.pwd)       # look in current working directory
config.filename = 'investments'   # file to search for

Find and read the configuration file:

config.read

You can also specify directly the file to read without setting up any search paths or filenames. If you specify a configuration with a known file extension, an appropriate format will be guessed, in this instance TOML:

config.read('./investments.toml')

In cases where you wish to specify a custom file extension, you will need to also specify the file format to use.

For example, if you have a configuration file formatted using YAML notation with extension called .config, to read it do:

config.read('investments.config', format: :yaml)

2.18 write

By default TTY::Config, persists configuration file in the current working directory with a config.yml name. However, you can change that by specifying the filename and extension type:

config.filename = 'investments'
config.extname = '.toml'

To write current configuration to a file, you can either specified direct location path and filename:

config.write('./investments.toml')

Or, specify location paths to be searched for already existing configuration to overwrite:

config.append_path(Dir.pwd)  # search current working directory

config.write

To create configuration file regardless whether it exists or not, use :force flag:

config.write(force: true)                        # overwrite any found config file
config.write('./investments.toml', force: true)  # overwrite specific config file

2.19 exist?

To check if a configuration file exists within the configured search paths use exist? method:

config.exist? # => true

2.20 autoload_env

The autload_env allows you to automatically read environment variables. In most cases you would combine it with env_prefix= to only read a subset of variables. When using autload_env, anytime the fetch is called a corresponding enviornment variable will be checked.

For example, given an evironment variable MYTOOL_HOST set to localhost:

ENV['MYTOOL_HOST']=localhost

And loading environment variables with a prefix of MYTOOL:

config.env_prefix = 'mytool'
config.autoload_env

You can retrieve value with:

config.fetch(:host)
# => 'localhost'

3. Examples

3.1 Working with env vars

TTY::Config fully supports working with environment variables. For example, there are couple of environment variables that your configuration is interested in, which normally would be set in terminal but for the sake of this example we assign them:

ENV['MYTOOL_HOST'] = '192.168.1.17'
ENV['MYTOOL_PORT'] = '7727'

Then in order to make your configuration aware of the above, you would use env_prefix= and set_from_env:

config.env_prefix = 'mytool'
config.set_from_env(:host)
config.set_from_env(:port)

or automatically load all prefixed environment variables with autoload_env:

config.env_prefix = 'mytool'
config.autoload_env

And then retrieve values with fetch:

config.fetch(:host)
#=> '192.168.1.17'
config.fetch(:port)
# => '7727'

3.2 Working with optparse

This is an example of combining tty-config with optparse stdlib.

Let's assume you want to create a command line tool that among many options accepts --host|-h and --port|-p flags. In addition, these flags will take precedence over the options specified in the configuration file.

First, you need to parse the flags and store results away in options hash:

require 'optparse'

options = {}

option_parser = OptionParser.new do |opts|
  opts.on("-h", "--host HOSTNAME_OR_IP", "Hostname or IP Adress") do |h|
    options[:host] = h
  end
  opts.on("-p", "--port PORT", "Port of application", Integer) do |p|
    options[:port] = p
  end
  opts.on("-c", "--config FILE",
         "Read config values from file (defaults: ./config.yml, ~/.config.yml") do |c|
    options[:config_file_path] = c
  end
  ...
end

option_parser.parse!

Then, you craete a configuration instance:

config = TTY::Config.new

And setup config filename:

config_filename = options[:config_file_path] || 'config.yml'

As well as add configuration file locations to search in:

config.append_path Dir.pwd
config.append_path Dir.home

Once config is initialized, you can read the configuration from a config file:

begin
  config.read(config_filename)  # by default the 'config.yml' is read
rescue TTY::Config::ReadError => read_error
  STDERR.puts "\nNo configuration file found:"
  STDERR.puts read_error
end

Then merge options passed as arguments with those stored in a configuration file:

config.merge(options)

Provide optional validation to ensure both host and port are configured:

if !config.fetch(:host) || !config.fetch(:port)
  STDERR.puts "Host and port have to be specified (call with --help for help)."
  exit 1
end

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/[USERNAME]/tty-config. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.

License

The gem is available as open source under the terms of the MIT License.

Code of Conduct

Everyone interacting in the Tty::Config project’s codebases, issue trackers, chat rooms and mailing lists is expected to follow the code of conduct.

Copyright

Copyright (c) 2018 Piotr Murach. See LICENSE for further details.