Using the COPY and NAME_IN built-in

Using the COPY and NAME_IN built-in functions in Forms isn't explained that well in the documentation. But they can be very useful in making your forms more generic by enabling you to build up field names dynamically and subsequently set and/or get the field values. In addition with the COPY function its possible to programatically insert non-numeric characters such as '%' into numeric fields, thus allowing wild-card searches to be performed.


NAME_IN

The name_in function allows you to get the value of a variable which itself is held as a variable name. Consider a form with two text fields on it - field1 and field2. Now into field1 enter the string 'Hello' and into field2 enter the string 'field1'. Now if you do a message(name_in(:field2)) it will display the string 'Hello'. As another example suppose you want to know what the value contained in the current form item is.
You look at the help and see that there is system variable called current_item. Great, I'll just message this out, however you'll soon discover that system.current_item is the name of the current item - not what it contains. To get at the value of the current item just enclose it within the name_in built-in - name_in(:system.current_item)


COPY


COPY is the complement of the NAME_IN function in that it allows you to set the value of a variable which itself is held as a variable. For example suppose you wish to set the value of the current item to the string 'Hello' - assuming the current item will be a text field. You can't simply do

:system.current_item:='Hello' ;

as Forms disallows this. But you can do a

COPY('Hello',:system.current_item);

Often you may have to dynamically create variables holding the name of fields on your form and set them to some value. Say you have 5 blocks - block1, block2 etc… all containing a text field of the same name - stock_id. To set the value of the stock_id field that the cursor is currently on you might use code like:-

COPY(' IBM',:system.current_block||'.stock_id');

One other use that COPY has is to place non-numeric characters into numeric fields programmatically during enter-query mode. Why would you want to do that? Mostly to allow the placing of wildcard characters such as '%'. You'll find that if you simply try:-

:num_field := '123%'

Forms will issue an error message

However doing COPY('123%',:num_field) works OK.

This only works during entry-query mode and you only need to use this if you have to enter the characters programmatically. You can just type in such characters normally if required.