Repositories, Contexts (Use Cases), Context Library

recoli.rb

# Establishing a top level namespace for a given module (Context Library),
# that serves as the internal API for a component of a system
# is a great way to begin the process of extracting that component
# from its containing environment.

# Benefits include:
# A well defined boundary of responsibilities
# More DRY (less duplicated knowledge of the way a component works)
# Isolates points of contact between component and containing system
# Expresses a clear and simple definition of the component's responsibilities defined by use case
# Autoloading in Ruby is a simple way to lazy load resources

# Downsides include:
# Slight learning curve (mostly when learning that component for the first time)
# Dependency injection can be abused
# Confidence in tests (where do you mock, where do you use real objects?)
# Trying to FP in an OOP context (this is actually a benefit in my humble opinion)

module ContextLibrary
  autoload :UseCase1, require 'lib/context_library/use_case1.rb'
  autoload :UseCase2, require 'lib/context_library/use_case2.rb'
  autoload :UseCase1Repository, require 'lib/repositories/use_case1.rb'
  autoload :UseCase2Repository, require 'lib/repositories/use_case2.rb'
  autoload :OtherDependency1, require 'lib/context_library/other_dependency1'
  autoload :OtherDependency2, require 'lib/context_library/other_dependency2'
  
  ...
  
  def self.use_case1
    UseCase1.new(use_case_1_repository, other_dependency_1)
  end
  
  def self.use_case2
    UseCase2.new(use_case_2_repository, other_dependency_2)
  end

  def self.use_case_1_repository
    UseCase1Repository.new
  end
  
  def self.use_case_2_repository
    UseCase2Repository.new
  end
  
  def self.other_dependency_1
    OtherDependency1
  end
  
  def self.other_dependency_2
    OtherDependency2
  end
  
  ...
  
end

# Defining UseCase1 as use case in the command pattern
module ContextLibrary
  class UseCase1
    def initialize(repository, other_dependency)
      self.repository       = repository              # <- emphasis spacing for Kevin Liddle ;)
      self.other_dependency = other_dependency
    end
    
    def call
      # relevant business logic
    end
    
    private
    
    attr_reader: :repository, :other_dependency
    
    # private methods
      
  end
end