[Rock-dev] Syskit::Composition child access within own methods

[Christian Rauch]

Hi,

in syskit I am inheriting from a composition, which relies on methods, 
that are not yet implemented in the base class:

{{{
     class TriggerIF < Syskit::Composition
         attr_accessor :name
         attr_accessor :sources
         attr_accessor :block

         def initialize(options)
             super(options)
             @trigger = nil
             @name = get_name
             @sources = get_sources
             @block = get_block
         end

         # add trigger
         on(:start) do |ev|
             @trigger = @rl.trigger(@name, @sources, @block)
         end

         # remove trigger
         on(:stop) do |ev|
             @rl.remove_trigger(@trigger)
         end

         def get_name
             puts "get_name: Implement me!"
             nil
         end

         def get_sources
             puts "get_sources: Implement me!"
             nil
         end

         def get_block
             puts "get_block: Implement me!"
             nil
         end
     end
}}}

In a composition derived from TriggerIF, these methods are defined:
{{{
     class GyroTrigger < Virgo::TriggerIF
         add Virgo::VectorDoubleTimedSrv, :as => 'sync'

         def get_name
             "gyro_trigger"
         end

         def get_sources
             sync_child.as(Virgo::VectorDoubleTimeSrv).vector_timed_port
         end
     end
}}}

The problem here is that 'sync_child' is not yet known when the 
Composition GyroTrigger is created:
{{{
Roby::NoSuchChild: gyro_trigger{}[] has no child with the role 'sync'
}}}

As the on(:start) of the base class is called first, I cannot define 
this in the on(:start) of the inheriting composition.

Is there a way to access own children within self define methods?
Or is there another way to tell the base class about the children and 
ports of the deriving class?

Regards,
Christian


-- 
  Christian Rauch
  Space Robotics

  Universität Bremen
  FB 3 - Mathematik und Informatik
  AG Robotik
  Robert-Hooke-Straße 5
  28359 Bremen, Germany

  Tel:     +49 (0)421 178 45-6619
  Empfang: +49 (0)421 178 45-6611
  Fax:     +49 (0)421 178 45-4150
  E-Mail:  Christian.Rauch at dfki.de

  Weitere Informationen: http://www.informatik.uni-bremen.de/robotik