GetChanges method (DataWindows)
Description
Retrieves changes made to a DataWindow or DataStore as a blob. This method
is used primarily in distributed applications.
Controls
|
DataWindow type |
Method applies to |
|---|---|
|
PowerBuilder |
DataWindow control, DataStore object |
|
Web ActiveX |
DataWindow control |
Syntax
[PowerBuilder]
|
1 |
long <span>dwcontrol</span>.<span>GetChanges</span> ( REF blob <span>changeblob</span> {, blob <span>cookie</span> } ) |
[Web ActiveX]
|
1 |
number <span>dwcontrol</span><span>.</span><span>GetChanges</span> (<span></span> ) |
|
Argument |
Description |
|---|---|
|
dwcontrol |
A reference to a DataWindow control or |
|
changeblob |
A variable into which the returned DataWindow In the Web ActiveX, call GetChangesBlob to |
|
cookie (obsolete) |
A read-only blob created by GetStateStatus that This argument is obsolete and will be disabled in |
Return Values
Returns the number of rows in the DataWindow change blob if
it succeeds and one of the following values if it fails:
-
–1 An internal
error occurred. -
–2 There is a conflict between
the state of the DataWindow change blob and the state of the DataWindow
from which the cookie was created; an attempt to use this blob in
a SetChanges call against the DataWindow will
fail. -
–3 There is a conflict between
the state of the DataWindow change blob and the state of the DataWindow
from which the cookie was created; but partial changes from the
change blob can be applied.
If any argument is null, the method returns null.
Usage
GetChanges is used in conjunction with SetChanges to
synchronize two or more DataWindows or DataStores. GetChanges retrieves
data buffers and status flags for changed rows in a DataWindow or
DataStore and places this information in a blob. SetChanges then
applies the contents of this blob to another DataWindow or DataStore.
Reapplying changes from one DataWindow (or DataStore)to another
If you call GetChanges on a DataWindow
and apply the data passed in the changeblob argument
to another DataWindow using SetChanges, you must
call GetChanges on the second DataWindow before
you reapply changes to it from the first DataWindow. The GetChanges call
on the second DataWindow updates the original timestamp on that
DataWindow so that it matches the current timestamp. (You cannot
use the Reset, ResetUpdate,
or AcceptText calls to update the original timestamp.)
If you try to reapply changes without first calling GetChanges on
the second DataWindow, you will get an error due to the conflict
between the state of the DataWindow changeblob and
the state of the second DataWindow.
The change blob created by GetChanges includes
only those rows that have a status of New!, NewModified!, or DataModified!.
For information about status values, see DWItemStatus.
Examples
These statements use GetChanges to
capture changes to a DataWindow control on a client. If GetChanges succeeds,
the client calls a remote object function that applies the changes
to a DataStore on the server and updates the database:
|
1 |
blob lblb_changes |
|
1 |
long ll_rv |
|
1 |
|
1 |
ll_rv = dw_employee.<span>GetChanges</span>(lblb_changes) |
|
1 |
|
1 |
IF ll_rv = -1 THEN |
|
1 |
MessageBox("Error", "GetChanges call failed!") |
|
1 |
ELSE |
|
1 |
iuo_employee.UpdateData(lblb_changes) |
|
1 |
END IF |