ON CHAIN-INPUT
Similar to ON INPUT. The ABAP module is called if any one
of the fields in the chain contains a value other than its initial
value (blanks or empty).
ON CHAIN-REQUEST
FOR EXAMPLE :
CHAIN.
FIELD: FIELD1, FIELD2.
FIELD: FIELD 3, FIELD 4.
MODULE X ON CHAIN-INPUT.
MODULE Y.
ENDCHAIN.
In the above code , module X is called only when value of any fields are entered other than initital value where as MODULE Y will be called, there is no condition attached to it.but , if MODULE Y has an error then it will open all the fields for input.
IF YOU WANT TO RESTRICT THE CONDITION ON PARTICULAR FIELD ,THEN ATTACH THAT MODULE NAME AFTER THAT FIELD .
CHAIN.
FIELD: BSEG-HKOT,BSEG-BUKRS MODULE X ON INPUT.
ENDCHAIN.
In this is case, MODULE X will be called only when BUKRS will have non-initial value , but if MODULE X finds an error, then both the fields will be opened for input again.
on chain request.
CHAIN.
FIELD: A, B, C MODULE X ON CHAIN-REQUEST.
ENDCHAIN.
AT EXIT COMMAND IN MODULE POOL
Sometimes, when we have obligatory fields(REQUIRED FIELD) input fields and we don't want to proceed further , and we want to come out of the program , it will not allow us. We have to enter the required value on screen fiels , then only we can come out of the screen , to overcome this problem,
we use AT EXIT-COMMAND at PAI of screen to force exit from screen without filling it .
