Refactor the MSH changes

We now restructure the code a little to group the MSH changes nicely. This is good practice for learning how to write a well-structured Translator script.

We do the following:

• Create a function called AlterMSH with the argument of an MSH segment
• Cut the existing statements altering the MSH segment and move them into this function
• Then call the function

Your screen should look something like this:

We need to change Out.MSH to MSH. We can do that by hand, or use the search and replace functionality in the Translator editor. Another good trick is to return MSH at the end of the function. This way it’s easy to see the MSH segment before and after we have altered it.

The code should now look like this:

And just to emphasize the point about comparing input and output of a function:

Here is the up-to-date code:

require 'split'
require 'zsegment'

local function trace(a,b,c,d) return end

function main(Data)
   local Orig = hl7.parse  {vmd = 'transform.vmd', data = Data}

   if Orig:nodeName() == 'Catchall' then
      iguana.logInfo('Filtered '..Orig.MSH[9][1]..'^'..Orig.MSH[9][2])
      return
   end

   local Out  = hl7.message{vmd = 'transform.vmd', name = Orig:nodeName()}

   Out:mapTree(Orig)
   local Copy = zsegment.copyZSegments(Data, Out:S())
   CheckTransform(Data:StripLastReturns(), Copy:StripLastReturns())

   AlterMSH(Out.MSH)

   trace(Out)
   local DataOut = Out:S()
   DataOut = zsegment.copyZSegments(Data, DataOut)
   DataOut = DataOut:StripLastReturns()
   trace(DataOut)
   queue.push{data = DataOut}
end

function AlterMSH(MSH)
   MSH[3][1] = 'Acme'
   MSH[4][1] = 'Lab'
   return MSH
end

function CheckTransform(Orig, Copy)
   if Orig ~= Copy then
      trace(Orig)
      trace(Copy)
      error('Copy of HL7 message does not match the original')
   end   
end

function string.StripLastReturns(S)
   -- strip return(s) "\r" & "\n" from the end of a string
   local i = #S
   while S:byte(i) == 10 or S:byte(i) == 13 do
      i = i - 1
   end
   return S:sub(1,i)
end