Using LSet to make reading files easier

Have you ever needed to read a fixed length text file in Visual Basic? I have written quite a lot of applications where I will receive a fixed length text file from the mainframe.
Tired of using the Left$, Right$ and Mid$ functions to parse each line for the individual elements of the line? Then read on.
Oh, and thanks to Rockford Lhotka's, book on Visual Basic 6 Business Objects for giving me this idea.

Original Author: Jerry Barnett

Code

Using the LSET keyword you can use a user defined type (UDT) to automatically parse a line from a text file into the individual elements......in ONE LINE OF CODE! Here is how:


First lets take a sample file (call it 'SOMEFILE.TXT'):

08072000Jerry M Barnett 0002356A2S56D9

Ok, the line above represents lets say one of a few hundred
lines. The layout of the file is as follows:




















































    Field  Type  Position  Remarks  
    Date  MMDDYYYY  1-8  Format will be MM/DD/YYYY  
    Name  AlphaNumeric  9-29  Padded with space  
    Amount  Numeric  30-36  9(5)v99    
    Code  Alpha  37  A for accepted,  
          R for rejected  
    Account  AlphaNumeric  38-43    

First thing is to create a user defined type representing the
layout of the file. (Note - this should be place in the Module
level of a program.)

















































    Type  udtInput      
      MyDate    As String * 8  
      Name    As String * 21  
      Amount    As String * 7  
      Code    As String * 1  
      Account    As String * 6  
    End  Type  

Note - All types are strings reguardless of
the type in the file. This will become clearer later. Next,
create a user defined type to represent the total length of the
line (I will explain why later)


























    Type  udtLine        
      strBuff  As String * 43      
    End  Type        

Now in your program you can do the following:

Sub Main()

' File Number

Dim iMyFile As Long

Dim sLine As udtLine

Dim sInput As udtInput

' Open your file for reading

Open App.Path & "SOMEFILE.TXT" for Input Access Read as #iMyFile

' Read the line into the udtLine UDT strBuff element

' This needs to be done, because you can't place a string

' directly into the UDT or you will get a type missmatch errorLine 

Input #iMyFile, sLine.strBuff

' The buffer (strBuff) represents the entire line

' Now copy the udtLine UDT (sLine) into the udtInput

' UDT (sInput) *** ONE LINE OF CODE! ***

LSet sInput = sLine

' Wolla! You can now access each element of the sInput UDT!

Debug.Print sLine.Name

' Will print: Jerry M Barnett

' (with eight trailing spaces)

' Convert numeric String Amount value to a Long value with 2 decimal places

Debug.Print CDbl(Val(sLine.Amount)/100)

' Would print: 23.56

Debug.Print MyDateFunction(sLine.MyDate)

' Will print: 08072000 in any format you wish

' Note - The MyDateFunction is a function you define

' to parse the date string to the proper format you want.

End Sub

That's it! Hope you find this of
use!

Note this can also be used (with
modification to' WRITE a flat file out.)

About this post

Posted: 2002-06-01
By: ArchiveBot
Viewed: 113 times

Comments

No comments have been added for this post.

You must be logged in to make a comment.

Field	Type	Position	Remarks
Date	MMDDYYYY	1-8	Format will be MM/DD/YYYY
Name	AlphaNumeric	9-29	Padded with space
Amount	Numeric	30-36	9(5)v99
Code	Alpha	37	A for accepted,
			R for rejected
Account	AlphaNumeric	38-43

Type	udtInput
	MyDate	As String * 8
	Name	As String * 21
	Amount	As String * 7
	Code	As String * 1
	Account	As String * 6
End	Type