Why are three segments listed when only one is present in the original message?

[Stratus3D]

For example, I have a normal HL7 message that contains one MSH segment at the beginning. When I parse the message msg[:MSH] is an array of three items.

f = open('example.hl7')
msg = HL7::Message.new(f)
msg[:MSH].class #=> Array
msg[:MSH].length #=> 3

Is there a reason this array contains three instances of HL7::Message::Segment::MSH? Is this a bug or is there a reason for this? I haven't spent a lot of time reading the code so I may be missing something here.

[gthiruva]

@Stratus3D A message is a collection of segments. In this case, that's msg. When you access msg[:MSH] you're selecting just one particular segment. So, when you calculate the length of just that one segment, you're getting a count of how many fields there are in the MSH segment.

For example, I'm looking at a result message from an immunization registry. So, it's a large message with 113 segments in it:

MSH|^~\&|CIR HL7 Web Service 2.01|NYC DOHMH|CAREDOX|0004Q10|20140529223528-0400||RSP^K11^RSP_K11|20140529223528-0400CIR-WS|T|2.5.1|||NE|NE|||||Z32^CDCPHINVS|
MSA|AA|hxe0P6tTzGBCqlIaWAcUBA|
QAK|QThxe0P6tTzGBCqlIaWAcUBA|OK|
QPD|Z34^Request ImmunizationHistory^HL70471|QThxe0P6tTzGBCqlIaWAcUBA||Mason^Matthew^Thomas^^^^L|Walters^Rebecca^^^^^M|20081025|M|305 BigApple Blvd&Big Apply Blvd&305^7C^NewYork^NY^12345-1234^^P|PRN^212^5551
PID|||777815087^^^^LR||MASON^MATTHEW^THOMAS^^^^L||20081015|M|
...

To count the segments, I apply the length method on the whole message:

[56] pry(main)> res.length
=> 113

And I get the expected 113 segments/lines. But if I select just the header segment, length() will count the number of vertical bar separated fields in :MSH:

[57] pry(main)> res[:MSH].length
=> 22