Distinguishing Between Null, Zero, Empty and Invalid in Fields

In Chameleon versions prior to 4.0, there was a problem in which the difference between 0 and Null in an HL7 message could not be distinguished in Java, Delphi and C#.

For example, when using the method, Table.getInteger(col, row), you would get a zero if the message did not have a value in the corresponding field in Java after parsing an incoming HL7 message.

To fix this issue for the different parser engines, two functions were added to Chameleon. The table below describes the two functions:

Parser Engine	Function Added	Description
3.211 to 4.5	IsNull	This function was added to Chameleon 4.0 to help distinguish between Null and Zero.
5.0 and later	GetState	This function was added to Chameleon 5.0 to help distinguish between Null, Zero, Empty and Invalid.

Note that the IsNull function is now deprecated in Parser Versions 5.0 and later (Options > Misc) and has been replaced with the GetState function. However, for backward compatibility reasons the IsNull function will still be available and supported for all previous parser versions.

IsNull vs. GetState

IsNull - If you are still using the 4.5 parser engine, it is recommended that you continue to use the IsNull function in your application since the GetState function may produce unwanted results.

GetState - If you are using the 5.0 parser engine, it is recommended that you use the new GetState function.

Usage examples are provided for each function and each supported language below:

Using the GetState Function

C++

enum State
{
   CHM_VALID = 0,
   CHM_PRESENT_BUT_NULL = 1,
   CHM_EMPTY = 2,
   CHM_INVALID = 3
};
   
// Test the value in the cell at row RowIndex and column ColumnIndex to see if it is null, zero, empty or invalid.
State GetState(size_t RowIndex, size_t ColumnIndex) const;

public enum State : int
{
   Valid = 0,
   PresentButNull = 1,
   Empty = 2,
   Invalid = 3,
}
   
// Test the value in the cell at row RowIndex and column ColumnIndex to see if it is null, zero, empty or invalid.
public State GetState(int columnIndex, int rowIndex);

Delphi

const CHM_TABLE_STATE_VALID = 0;
const CHM_TABLE_STATE_PRESENT_BUT_NULL =  1;
const CHM_TABLE_STATE_EMPTY = 2;
const CHM_TABLE_STATE_INVALID =  3;

// Test the value in the cell at row RowIndex and column ColumnIndex to see if it is null, zero, empty or invalid. 
function GetState(RowIndex, ColumnIndex :  Integer) : Integer;

Java

package com.interfaceware.chameleon;
 
public class TableState
{
    public static final int Valid = 0;
    public static final int PresentButNull = 1;
    public static final int Empty = 2;
    public static final int Invalid = 3;
}
    
// Test the value in the cell at row RowIndex and column ColumnIndex to see if it is null, zero, empty or invalid.
public int getState(int ColumnIndex, int RowIndex) throws ChameleonException;

Using the IsNull Function