Using the CASE command with OR operations
Using the CASE command with operations other than "=" (equal to)
Using the CASE command with compound expressions
This example illustrates the most basic type of CASE command processing.
Imagine that a user inputs a value into field #DEPTMENT and that a CASE command to be used to implement this logic:
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Structurally, a CASE command to implement this logic would look like this:
CASE OF_FIELD(#DEPTMENT)
WHEN VALUE_IS('= ADM')
<< Logic >>
WHEN VALUE_IS('= AUD')
<< Logic >>
WHEN VALUE_IS('= FLT')
<< Logic >>
WHEN VALUE_IS('= TRVL')
<< Logic >>
OTHERWISE
<< Logic >>
ENDCASE
A sample program to fully implement this logic might be coded like this:
BEGIN_LOOP
REQUEST FIELDS(#DEPTMENT (#SECTION *OUTPUT))
CASE OF_FIELD(#DEPTMENT)
WHEN VALUE_IS('= ADM')
CHANGE FIELD(#SECTION) TO(A)
MESSAGE MSGTXT('ADM was entered')
WHEN VALUE_IS('= AUD')
CHANGE FIELD(#SECTION) TO(B)
MESSAGE MSGTXT('AUD was entered')
WHEN VALUE_IS('= FLT')
CHANGE FIELD(#SECTION) TO(C)
MESSAGE MSGTXT('FLT was entered')
WHEN VALUE_IS('= TRVL')
CHANGE FIELD(#SECTION) TO(D)
MESSAGE MSGTXT('TRVL was entered')
OTHERWISE
CHANGE FIELD(#SECTION) TO(E)
MESSAGE MSGTXT('Other value was entered')
ENDCASE
END_LOOP
Imagine you have to implement this logic:
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If you code nested IF-ELSE-END blocks you will end up with logic like this:
IF COND('(#DEPTMENT = ADM) or (#DEPTMENT = FLT) or (#DEPTMENT = TRVL)')
CHANGE FIELD(#SECTION) TO(A)
MESSAGE MSGTXT('Either ADM , FLT or TRVL was entered')
ELSE
IF COND('(#DEPTMENT = AUD) or (#DEPTMENT = INF) or (#DEPTMENT = MKT)')
CHANGE FIELD(#SECTION) TO(B)
MESSAGE MSGTXT('Either AUD, INF or MKT was entered')
ELSE
CHANGE FIELD(#SECTION) TO(C)
MESSAGE MSGTXT('Other value was entered')
ENDIF
ENDIF
However, by using a CASE command you can code this instead:
CASE OF_FIELD(#DEPTMENT)
WHEN VALUE_IS('= ADM' '= FLT' '= TRVL')
CHANGE FIELD(#SECTION) TO(A)
MESSAGE MSGTXT('Either ADM, FLT or TRVL was entered')
WHEN VALUE_IS('= AUD' '= INF' '= MKT')
CHANGE FIELD(#SECTION) TO(B)
MESSAGE MSGTXT('Either AUD, INF or MKT was entered')
OTHERWISE
CHANGE FIELD(#SECTION) TO(C)
MESSAGE MSGTXT('Other value was entered')
ENDCASE
Which is shorter, easier to read and easier to maintain. It also executes faster in most situations.Using the CASE command with OR operations
Imagine that when field #TEST contains A or B or C you have to perform some operation.
If it contains X or Y or Z you have to perform some other operation.
If it contains any other value it all then you have to perform yet another operation.
You could use a CASE command structured like this to implement the required logic:
CASE OF_FIELD(#TEST)
WHEN VALUE_IS('= A' '= B' '= C')
<< Logic Block 1 >>
WHEN VALUE_IS('= X' '= Y' '= Z')
<< Logic Block 2>>
OTHERWISE
<< Logic Block 3>>
ENDCASE
Using the CASE command with operations other than "=" (equal to)
Imagine that when field #COPIES needs to be validated according to these rules:
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Hence a CASE command can be used like this:
DEFINE FIELD(#COPIES) TYPE(*DEC) LENGTH(3) DECIMALS(0) EDIT_CODE(N) DEFAULT(+1)
BEGIN_LOOP
REQUEST FIELDS(#COPIES)
CASE OF_FIELD(#COPIES)
WHEN VALUE_IS('= 0')
MESSAGE MSGTXT('Value of zero is invalid')
WHEN VALUE_IS('< 0')
MESSAGE MSGTXT('Value is negative')
WHEN VALUE_IS('<= 50')
MESSAGE MSGTXT('Value is sensible')
OTHERWISE
MESSAGE MSGTXT('Value is probably incorrect')
ENDCASE
END_LOOP
Using the CASE command with compound expressions
In a situation whereby a field #DISCOUNT needs to be validated by using a mathematical calculation such as this:
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This can be coded by using the CASE command:
DEFINE FIELD(#DISCOUNT) TYPE(*DEC) LENGTH(11) DECIMALS(2) EDIT_CODE(1)
DEFINE FIELD(#QUANTITY) TYPE(*DEC) LENGTH(3) DECIMALS(0)
BEGIN_LOOP
REQUEST FIELDS(#DISCOUNT #QUANTITY)
CASE OF_FIELD(#DISCOUNT)
WHEN VALUE_IS('> (#QUANTITY * 0.1)')
MESSAGE MSGTXT('Discount value is larger than quantity times 0.1')
WHEN VALUE_IS('< (#QUANTITY * 0.1)')
MESSAGE MSGTXT('Discount value is less than quantity times 0.1')
OTHERWISE
MESSAGE MSGTXT('A correct discount value was entered')
ENDCASE
END_LOOP
