INPUT ARRAY behavior

This topic describes INPUT ARRAY differences between I4GL and Genero BDL.

DISPLAY TO and field modification flag

During an INPUT ARRAY dialog, to change the value of a form field by program, existing code typically sets the value in the program array field, and then displays this value to the corresponding form field with:

DISPLAY prog-array[arr_curr()].colname
   TO screen-array[scr_line()].fieldname

In such case, IBM® Informix® 4GL will not mark the field as modified, while Genero BDL will set the modification flag of the field, like when the user modifies the field interactively.

As result, with Genero BDL, the row is considered as modified by the user, and row validation will occur as if the user entered the value, while I4GL will consider the displayed value as valid, even if it does not fullfill the form constraints, allowing the user navigate in the record list without correcting invalid data.

This behavior has also an impact on new temporary rows created at the end of the list: If the user does not enter values or when no DISPLAY TO is performed, the temporary row disappears when moving back in the list. If a DISPLAY TO is used, the row is touched and will remain in the list.

When setting a form field value by program, the value should always satisfy field constraints.

Best practice to change the data visible to the user is to configure the INPUT ARRAY dialog with the The buffered and unbuffered modesUNBUFFERED attribute. This way, changing the program array will automatically sync the form fields, without the need to use a DISPLAY TO instruction, and without setting the field modification flag.

INCLUDE constraint behavior

When defining a form field with an INCLUDE list and without a NOT NULL constraint, for example:

f1 = FORMONLY.f1 TYPE CHAR, INCLUDE = ("a","b");

During an INPUT ARRAY, when modifying an existing row, IBM Informix 4GL allows the user to empty the field with a space. With Genero BDL, the user must enter one of the values listed in the INCLUDE attribute.

Consequently, I4GL allows the the end-user to clear such fields on existing rows, but forces the field be not be null when creating new rows, which is not consistent.

The Genero BDL behavior is consistent, while the I4GL behavior can be considered as a bug.

Best practice is to add a NOT NULL constraint on the field, to make sure that the field must contain one of the values defined by the INCLUDE list.