RAD Studio VCL Reference
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Implements a virtual method for positioning the dataset on the previous record, respecting any filters.
function FindPrior: Boolean;
__fastcall Boolean FindPrior();
This function returns false, indicating that the active record was not successfully changed. Descendant classes override FindPrior to move to the previous record of the dataset, honoring any filters that are in effect. In descendants, FindPrior returns true if the active record is successfully changed.
Delphi Examples:
{ This example uses a button to copy the value of a field in the previous record into the corresponding field in the current record. } procedure TForm1.Button1Click(Sender: TObject); var SavePlace: TBookmark; PrevValue: Variant; begin with Customers do begin { get a bookmark so that we can return to the same record } SavePlace := GetBookmark; try { move to prior record} FindPrior; { get the value } PrevValue := Fields[1].Value; {Move back to the bookmark this may not be the next record anymore if something else is changing the dataset asynchronously } GotoBookmark(SavePlace); { Set the value } Edit; Fields[1].Value := PrevValue; { Free the bookmark } finally FreeBookmark(SavePlace); end; end; end; { To ensure that the button is disabled when there is no previous record, the OnDataChange event of the DataSource detects when the user moves to the beginning of file (BOF property becomes true), and disables the button. Detection occurs on scrolling and editing, not selection with the mouse. } procedure TForm1.DS2DataChange(Sender: TObject; Field: TField); begin if Customers.Bof then Button1.Enabled := False else Button1.Enabled := True; end;
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