A Quick Dependency Injection Example

gistfile1.rb

class GetMessageFromQueue

  def initialize(options)
    @queue = options.fetch(:queue)
  end

  def call
    @queue.pop
  end

end

class RemoteQueue

  def initialize(settings)
    @settings = settings
  end

  def pop
    connection.fetch_message
  end

  private

  def connection
    # do some stuff with the settings
  end

end


queue = RemoteQueue.new(url: "http://localhost", token: "abc")
get_message = GetMessageFromQueue.new(queue: queue)

message = get_message.call

Very nice.

Are you using a Service Locator for setting up the dependencies?
The manual setup (lines #32-33) can get reasonably complicated when you have several dependencies I guess.

I rewrote a piece of code to this style. Would this make sense? I am doubting passing the class instead of passing an instance here (the methods would need an argument then). Passing the instance seems the way to go in this case, what do you think?

class RetrievesJenkinsInformation

  def initialize(project, options)
    @project = project
    @retrieves_job = options.fetch(:job_retriever)
    @mapper = options.fetch(:build_status_mapper)
  end

  def update
    { :status => @mapper.new(job.color).map }
  end

  def jenkins
    @project.jenkins
  end

  def job
    @retrieves_job.new(jenkins.identifier).retrieve
  end
end

project = ... # ActiveRecord call
options = {
  job_retriever: Jenkins::Job,
  build_status_mapper: MapsJobColorToBuildStatus
}
updated_information = Jenkins::RetrievesJenkinsInformation.new(project, options)