readme.md

Domain Specific Language (DSL)

Introduction

In this workshop we're going to build a DSL (domain specific language) to parse the employee hierarchy of a company. Using a top level company method we're going to define the data, then use the same method to output that information to the console.

Example Usage

The DSL for defining the data will look like this:

company do

  department 'Development' do

    employee do
      first_name 'Josh'
      last_name 'Nesbitt'
      role 'Software Engineer'
    end

    employee do
      first_name 'Leon'
      last_name 'Davis'
      role 'Software Engineer'
    end

  end

  department 'Management' do

    employee do
      first_name 'Tracy'
      last_name 'Myers'
      role 'Scrum Master'
    end

  end

end

And once the DSL has been parsed it will make the data available as objects like this:

company.departments.each do |department|

  puts department.name

  department.employees.each do |person|

    puts "  #{person.first_name} #{person.last_name}: #{person.role}"

  end

end

Which should output:

Development
  Josh Nesbitt: Software Engineer
  Leon Davis: Software Engineer
Management
  Tracy Myers: Scrum Master

Walk-through

Coding walk-through to be done in person with group.

Solutions

• Building and parsing the DSL

Extensions

The current DSL is great, but somewhat limited. We want to be able to declare the Managing Director of the company. For this exercise, we'll assume that the MD is an existing employee.

Assume we want to declare the MD like so:

employee do
  managing_director

  first_name 'Tracy'
  last_name 'Myers'
  role 'Scrum Master'
end

To be fetched like so:

company.managing_director # => Employee object

This should return an employee object, just like department.employees.first. How would you do this?