TDataSet.Post Method

Implements a virtual method to write a modified record to the database or change log.

Pascal

procedure Post; virtual;

C++

virtual __fastcall Post();

Description

TDataSet implements a virtual method to write a modified record to the database or change log. Dataset methods that change the dataset state, such as Edit, Insert, or Append, or that move from one record to another, such as First, Last, Next, and Prior automatically call Post.

Different types of datasets handle posting differently:

BDE-enabled datasets post records directly to the database server unless CachedUpdates is true. When caching updates, BDE-enabled datasets post records to an internal change log until they are applied to the database by calling ApplyUpdates.

ADO and InterBaseExpress datasets post records directly to the database server.

Client datasets post records to an internal change log until they are applied to the database by calling ApplyUpdates or merged with the client dataset's data by calling MergeChangeLog.

Unidirectional datasets are read-only and do not post records at all.

Designers of custom datasets can choose whether to implement Post by writing records to the database server or to an internal change log.

Delphi Examples:

Copy Code

{
This example appends a new record to a table or client
dataset when the user clicks a button. The two fields
Field1 and Field2 are filled from the contents of two edit
controls.  This example requires a populated TTable or
TDataSet with the appropriate field values.
} 
procedure TForm1.Button1Click(Sender: TObject);
begin
  Customers.Append;
  Customers.FieldValues['Field1'] := StrToInt(Edit1.text);
  Customers.FieldValues['Field2'] := Edit2.text;
  Customers.Post;
end;

Copy Code

{
The following fragment prompts the user to confirm changes
to a record; if the user clicks Yes, the record is posted to
the table, otherwise the changes are cancelled.
} 
procedure TForm1.Button2Click(Sender: TObject);
begin
if MessageDlg('Update Record?', mtConfirmation, [mbYes, mbNo], 0) =
              mrYes then
  Table1.Post
else
  Table1.Cancel; 
end;