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C++Builder Database Architecture
Table 12.20. TDataSource key methods.
Method Function
Edit Switches the associated TDataset into Edit mode.
Table 12.21. TDataSource key events.
Event Catalyst
OnDataChange Occurs when data is changed or the record pointer moves.
OnStateChange Occurs when the State property changes.
OnUpdateData Occurs when Post or UpdateRecord is called.
Key Elements
The TDataset property identifies the TTable, TQuery, or TStoredProc that supplies the
component with data. The AutoEdit property determines whether modifying the contents
of a data-aware control will automatically switch the TDataset into Edit mode, allowing
changes to be made to the underlying data.
Tasks
You can monitor changes to a TDataset and its associated data-aware controls by assigning
an event handler to the OnDataChange event.
The OnStateChange event occurs when the State of the TDataset changes. For example, if you
switch the TDataset’s State from dsBrowse to dsEdit by calling the Edit routine, this event
will be triggered. Because OnStateChange can occur for nil TDatasets, be sure to check for a
nil TDataset before attempting to reference it.
If you want to change the data in the current row before it is posted, set up an OnUpdateData
event. It’s triggered when Post or UpdateRecord is called.
TUpdateSQL
Module: DBTables Class ancestor: TDataSetUpdateObject
The TUpdateSQL component enables you to control the way that TDatasets are updated.
Because you have complete control over the update process, you can even update read-only
TDatasets. You do this via TUpdateSQL’s InsertSQL, DeleteSQL, and ModifySQL properties,
which allow you to specify the SQL to execute for row insertions, deletions, and updates.
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