Torihiki

Introduction

Torihiki is a DSL for building business transactions built using a concept of function composition.

Torihiki doesn’t include error handling out of the box as it dry-transaction does, but you feel free to use Either from dry-monad or anything else for it.

What exactly is the function composition?

Function composition is applying result of a function as an argument to the next one in a chain.

For example, we have functions F and G and a context x. The composition G of F of x, would look like G(F(x)). In other words result of F(x) will be received by G as an argument. We also could say that G is composed with F or G is after F. In algebra it could be written like:

G(F(x)) = (G ∘ F)(x)

How is this theory related to the subject?

Transactions in common are just an ordered actions around context we could think about as a single object. Function composition is the same thing from this point of view.

Installation

Add gem to your Gemfile

gem 'torihiki', '~> 0.1.0'

Run bundle install
Do great things!

Usage

Simple transaction

Lets do very silly SquareOfSumTransaction which gets a hash with keys x and y with numeric values and returns a square if their sum. It is not a real life example but it help us explore the DSL.

Torihiki is a module which expects you to include it into your class:

class SquareOfSumTransaction
  include Torihiki
end

Now we need to create some operations. The simpliest way to do it is call map method and provide implementation.

Method map accepts a block, proc, lambda or object which has method call implemented.

class SquareOfSumTransaction
  include Torihiki

  map { |context| context[:x] + context[:y] }
  map { |sum| sum ** 2 }
end

And now lets do the calculations.

SquareOfSumTransaction.call(x: 1, y: 2) # => 9
SquareOfSumTransaction.call(x: 3, y: 5) # => 64

Torihiki remembers sequence of map calls. When we send call with a context to transaction class it will execute first block using the it. Result of the first block call will be provided to the second one as a parameter and so on. Result of the last one will be returned.

Contribution Guide

Just add pull request =)