Services and Dependency Injection in Ruby

gistfile1.rb

class Discussion
  def initialize(roundtable, resources_proc, themes_proc)
    @subject = roundtable.subject
    @body = roundtable.body
    @resource_proc = resources_proc
    @themes_proc = themes_proc
  end

  def resources
    @resources_proc.call
  end
    
  def themes_proc
    @themes_proc.call
  end

end

class LazyLoadService
  def get_discussions(*args)
    roundtable = Roundtable.find(1)
    Discussion.new(roundtable, lambda{ get_resources }, lambda{ get_themes })
  end

  def get_resources

  end

  def get_themes

  end

end

class NotLazyLoadedService
  def get_discussions(*args)
    roundtable = Roundtable.find(1)
    Discussion.new(roundtable, get_resources, get_themes)
  end

  def get_resources

  end

  def get_themes

  end
end

Can you show me how you'd consume these objects? I'm wondering why we could not just sub-class this out, or pass in optional constructor arguments/hash to get a similar outcome.

what do you mean how the objects would be consumed?

I think subclassing this Discussion class is an option but not optimal as this would require you subclass for each different way of handling the the internalized collections.

The point of the Discussion class is to provide a contract layer for interacting with the data from the domain.

You could also pass in option constructor args - such as if a collection is passed in, then use the passed in collection or pull it from somewhere off the "roundtable" argument passed in but then you do not allow the option of lazy loading from multiple sources.

This code allows you to lazy load or eager load and you can do it from any source the particular service determines as acceptable.

The result of the procs passed in must respect a common interface however.