Arvados

Radhika to write a list of method signatures that we need. In order to implement the views that we currently have, write a list of method signatures for our work units (including names of methods, and the list of their arguments), and the return value of each of those methods.

Some notes about the ruby language specific aspects of this implementation.

• There is no support for inheriting behavior from multiple sources (interfaces)
  • So, we can’t do: Job < ArvadosBase, WorkUnit

• Instead we can do something like this:
  

  class WorkUnit < ArvadosBase
     def child_work_units
       raise "Not implemented" 
     end
  end
  
  class Job < WorkUnit (instead of current Job < ArvadosBase)
  
  

• Only when the “child_work_units” method is invoked, the exception is raised. That is, just by declaring that Job implements WorkUnit, we will not get the exception (as in a java interface). Instead, only when we stumble upon it, we get the exception.

• Tom: Is this the strategy we are planning to use?

We should document the work unit interface -- perhaps in app/models/work_unit.rb, in a class called WorkUnit. (In Ruby, an interface essentially is just documentation.)

Each object we intend to display using a generic work unit view/partial must have a "work_unit" method that returns an object that satisfies the work unit interface.

class Job
  def work_unit label
    JobWorkUnit.new(self, label)
  end
end

class WorkUnit
  # This is just an abstract class that documents the WorkUnit interface; a
  # class can implement the interface without being a subclass of WorkUnit.
  def label
    # returns the label that was assigned when creating the work unit
  end
  def uuid
    # returns the arvados UUID of the underlying object
  end
  def children
    # returns an array of child work units
  end
end

class ProxyWorkUnit < WorkUnit
  def initialize proxied, label
    self.label = label
    self.proxied = proxied
  end
  def label
    self.label
  end
  def uuid
    self.proxied.uuid
  end
end

class JobWorkUnit < ProxyWorkUnit
  def children
    n = -1
    self.proxied.job_tasks.map do |t|
      n++
      t.work_unit("task #{n}")
    end
  end
end