Mandate

A simple command-pattern helper gem for Ruby.

Note: As of 2.0.0, Mandate only supports Ruby 3.x. For Ruby 2.x, please use the 1.0.0 release.

Installation

Add this line to your application's Gemfile:

gem 'mandate'

And then execute:

$ bundle

Or install it yourself as:

$ gem install mandate

Usage

class Multiplies
  include Mandate

  initialize_with :number_1, number_2: 0

  def call
    do_the_maths
  end

  # Memoize any method by putting the keyword before it.
  memoize
  def do_the_maths
    sleep(10)
    number_1 * number_2
  end
end

# This calls initializer and then call with the params
Multiplies.(20, 3)
# => 60

`initialize_with`

The initialize_with method creates an initializer and private attr_readers for the specified variables. Keyword arguments can be expressed normally, but arguments without default values must be specified with the value Mandate::NO_DEFAULT. You may also use the Mandate::KWARGS param to capture any params that aren't explicitely set. The call also takes a block, which is run after the variables are set.

For example, this...

MODELS = ...

class Car
  initialize_with :model, color: "blue", owner: Mandate::NO_DEFAULT, params: Mandate::KWARGS do
    raise unless MODELS[model].colors.include?(color)
  end
end

...is the equivalent of...

MODELS = ...

class Foobar
  def initialize(model, color: "blue", owner:, params = {})
    @model = model
    @color = color
    @owner = owner
    @params = params

    raise unless MODELS[model].colors.include?(color)
  end

  private
  attr_reader :model, :color, :owner
end

Using on_success/on_failure callbacks

Sometimes it is helpful for the class to return on_success/on_failure callbacks rather than just the resulting value. This can be achieved by including the Mandate::Callbacks module as follows:

class Sumer
  include Mandate
  include Mandate::Callbacks

  initialize_with :num1, :num2

  def call
    abort!("num1 must be an Integer") unless num1.is_a?(Integer)
    abort!("num2 must be an Integer") unless num2.is_a?(Integer)

    num1 + num2
  end
end

res = Sumer.(1,2)
res.on_success { |result| p result } # puts 3
res.on_failure { |errors| p errors } # Noop
res.succeeded? # true
res.result # 3
res.errors # []

res = Sumer.("1","2")
res.on_success { |result| p result } # Noop
res.on_failure { |errors| p errors } # puts ["num1 must be an Integer"]

res = Sumer.("1","2")
res.on_failure { |errors| p errors } # puts ["num1 must be an Integer", "num2 must be an Integer"]
res.errors # ["num1 must be an Integer", "num2 must be an Integer"]

It is also possible to chain methods, for example:

Sumer.(1,2).
  on_success { |result| p result }.
  on_failure { |errors| p errors }

The succeeded? method is also aliased as success?.

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake test 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/iHiD/mandate.