ruby-hl7 - creating a new segment classWed, Apr 11, 2007 dev
Ok, so you want to do something more than muck with some fields in passing segments. Ruby-hl7 provides a nice way to encapsulate specific segments as objects, dealing with field aliases instead of field id numbers. After all isn’t my_obj.last_checkup_date a little clearer than my_obj.e11. I certainly think so, which is why you can define a class for a segment type. Let’s create a class describing a BLG (Billing) segment.
# When a message is parsed, the parser checks for a class matching this format class HL7::Message::Segment::BLG < HL7::Message::Segment weight 600 # we want this to go after every other segment (they are sorted ascendingly) # we're adding a field alias to BLG.1, which happens to be "when to charge" in the docs add_field :name=>:when_to_charge # we'll include some value checking logic in the next field we add VALID_CHARGES = %w[ CH CO DR DP GR NC NP RS ] add_field :name=>:charge_type do |c| raise HL7::Exception.new("Invalid charge type") unless c raise HL7::Exception.new("Invalid charge type") unless VALID_CHARGES.index(c) c # we need to return the final value of c as this is called on read/write end # we can explicitly set the field id, this would point to BLG.4 add_field :name=>:charge_type_reason, :idx=>4 end
Now let’s use it:
# create the empty hl7 message msg = HL7::Message.new # create our segments and fill in some data msh = HL7::Message::Segment::MSH.new blg = HL7::Message::Segment::BLG.new blg.when_to_charge = Date.new.to_s blg.charge_type = "CH" msg << msh msg << blg
There you go, the suggested method for dealing with known segments.