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. . . GET SYSTEM OVERVIEW . . .
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The GET SYSTEM is an extension of the CA-Clipper GET system with an
extensive number of new features.
The GET SYSTEM has introduced the use of BUTTONs, CHECK BOXES, LISTBOXES
and RADIO BUTTONS as data collection and display objects (READERs). The use
of these extensions are seamless and easy to encorporate into existing
systems.
In addition to the new READERs, extensions have been added to the STANDARD
READER. Clauses have been added for MESSAGEs, MASTERVAR, MASTERAREA,
LIST, DBLIST, USERLIST and HIDDEN.
The MESSAGE clause is used to associate a message with a GET.
There are two approaches to record locking: prelock and postlock. In the
prelock scenario the record is locked, the data is copied, edited, replaced
and then unlocked. In the postlock scenario the data is copied and edited,
the record is locked and the data is replaced. However, for the postlock
scenario to work, an image of the data record must be taken at edit time and
then prior to replacing the data, the data record is compared to the stored
image to see if the record was changed by another user. The only problem
with the postlock scenario is when the record data has changed, causing
appropriate action to be taken. The postlock scenario is the appropriate
way to contol record locking in an event driven environment. In the prelock
scenario the problem arises in controlling the length of time the user has
the record locked. In both cases the data from a database field is generally
copied to a memory variable and then edited. MASTERVAR and MASTERAREA
clauses are used to associate a GET to the original database field and work
area where the data came from. By associating a GET to a specific data
field the postlock scenario can be easily programmed through the use of the
OrigChanged() function. When a data save process is called it easily checks
the data source to see if the data has changed, taking action if required.
The LIST, DBLIST and USERLIST clauses associate a choice list to the
GET. A . character is automatically attached to the right end of the
GET. By clicking on the list character with the mouse or hitting the list
key, the defined list will be called. ANY DBF TO BE OPENED IN A DBLIST THAT
IS ALREADY OPEN MUST HAVE BEEN OPENED IN SHARED MODE (SET EXCLUSIVE OFF).
The HIDDEN clause causes the GET to disappear when the WHEN clause
returns a false. This is useful in security situations where data must be
hidden from certain users.
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