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Objects are functions! Treat any Object or Class as a Proc (like Enumerable but for Procs)


Objects that enclose state, can be treated as automatically curried functions.

require 'invokable'

class TwitterPoster
  include Invokable

  def initialize(model)
    @model = model

  def call(user)
    # do the dirt
    ..., data)
end # => #<TwitterPoster ...>, current_user) # => #<TwitterStatus ...>

# both the class and it's instances can be used anywhere Procs are.

Model.where(created_at: # => [#<TwitterPoster ...>, ...]

Use memoize, << and >> for composition and other methods on Proc on your command objects

# app/queries/filter_records.rb
class FilterRecords
  include Invokable

  def initialize(params)
    @params = params

  def call(records)
    # do filtering return records

# app/queries/sort_records.rb
class SortRecords
  include Invokable

  def initialize(params)
    @params = params

  def call(records)
    # do sorting return records

sort_and_filter = << # => sorted and filtered records

Helper methods that can be used with any object that responds to call or to_proc

Invokable.juxtapose(:sum, -> (xs) { xs.reduce(:*) }, :min, :max).([3, 4, 6]) # => [13, 72, 3, 6]

Invokable.knit(:upcase, :downcase).(['FoO', 'BaR']) # => ["FOO", "bar"]

They are also mixed into any class that includes the module

class Transformer
  include Invokable

  def call(array), compose(:to_s, :upcase))).to_h
end[:a, :b, :c, :d]) # => {:a => "A", :b => "B", :c => "C", :d => "D"} 

Hashes can be treated as functions of their keys

require 'invokable'
require 'invokable/hash'

number_names = { 1 => "One", 2 => "Two", 3 => "Three" }
[1, 2, 3, 4].map(&number_names) # => ["One", "Two", "Three", nil]

Arrays can be treated as functions of their indexes

require 'invokable'
require 'invokable/array'

alpha = ('a'..'z').to_a
[1, 2, 3, 4].map(&alpha) # => ["b", "c", "d", "e"]

Sets can be treated as predicates

require 'invokable'
require 'invokable/set'

favorite_numbers = Set[3, Math::PI]
[1, 2, 3, 4].select(&favorite_numbers) # => [3]

Use as much or a little as you need

require 'invokable'         # loads Invokable module
require 'invokable/helpers' # loads Invokable::Helpers module
require 'invokable/hash'    # loads hash patch
require 'invokable/array'   # loads array patch
require 'invokable/set'     # loads set patch
require 'invokable/data'    # loads hash, set and array patches


A function is a mapping of one value to another with the additional constraint that for the one input value you will always get the same output value. So, conceptually, Ruby Hashes, Arrays, and Sets are all functions. Also, there are many one method objects out there (e.g. Service Objects) that are essentially functions. Why not treat them as such?


Add this line to your application’s Gemfile:

gem 'invokable'

And then execute:

> bundle

Or install it yourself as:

> gem install invokable

API Documentation

See Also


Tested using MRI 2.4, 2.5, 2.6, 2.7, 3.0 and JRuby


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