component acts as a bridge between one dataset component ( TTable in this case) and one or more data-aware controls that provide a visible interface to data...

Table 2.2
Important TDataSource properties for a single-table form
Property
Value
Remarks
AutoEdit
True (default)
When AutoEdit is True, Delphi puts the TDataSource into Edit state
automatically when the user changes a value in a linked control.
To make a TDataSource read-only, or to control when to enter Edit state,
set AutoEdit to False.
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D a t a b a s e A p p l i c a t i o n D e v e l o p e r ’ s G u i d e
Table 2.2
Important TDataSource properties for a single-table form (continued)
Property
Value
Remarks
DataSet
Table1
Specifies which TTable (or TQuery) is supplying the data.
Name
DataSource1
Use the Object Inspector to change names.
The form contains one TDBGrid control. The expert links it to a TDataSource component by setting the properties listed in the following table. By default, a TDBGrid includes all the fields (columns) in a table. To limit the columns displayed by a TDBGrid, double-click on its associated TTable component to invoke the Fields Editor (see page 30).
Table 2.3
Important TDBGrid properties for a single-table form
Property
Value
Remarks
DataSource
DataSource1
Links the DBGrid control to a TDataSource component, which
supplies the data.
The form contains one TDBNavigator control. This control moves a table’s current record pointer forward or backward, starts Insert or Edit state, posts new or modified records, etc. The expert links this control to the Parts table by setting the properties listed in the following table.
Table 2.4
Important TDBNavigator properties for a single-table form
Property
Value
Remarks
DataSource
DataSource1
Links the control to a TDataSource
component.
VisibleButtons
A list of button identifiers and a
For example, by default nbNext is True, so the
corresponding Boolean value that
Next Record button is visible; nbDelete is
specifies whether that button is visible. False, so the Delete button is invisible.
Example: nbFirst True.
The expert does more than create a form and components. It also generates a line of code to open the table at run time in case you do not activate the table at design time. For
example, the expert creates TTable components with the Active property set to False.
That’s why the various TDBEdit controls aren’t displaying data. You could set Active to True, and the controls would display data from the first record. Instead, the Form
Expert generates the following code to open the table at run time.
procedure TEditPartsForm.FormCreate(Sender: TObject);
begin
Table1.Open;
end;
This code is hooked to the form’s OnCreate event, so Delphi executes it before creating the form. As a result, the table is opened before the form is displayed.
Note
Code created by the Form Expert is like code you type yourself. If you rename
components created by the expert, be sure to update your source file everywhere the
renamed component occurs. Name changes to components that Delphi originates (for
example, in the type declaration) are changed automatically for you by Delphi.
C h a p t e r 2 , B u i l d i n g a s a m p l e d a t a b a s e a p p l i c a t i o n : M A S T A P P
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For more information
For more information about
• Building Delphi forms, see the User’s Guide.
• Naming components, see the User’s Guide.
• The Delphi database architecture, see Chapter 1, “Introduction.”
• TTable components, see page 8.
• The Fields Editor, see page 30.
• TDataSource components, see page 10.
Building a master-detail form
The steps in this section show how to use the Database Form Expert to build a form
containing two tables: a master table and a detail table, linked one-to-many. This form
is the basis for the CUSTORD.DFM form in MASTAPP. The master table is
CUSTOMER.DB and the detail table is ORDERS.DB. You can access both tables using
the MAST alias. The expert links these tables and creates components to display data for one customer at a time, and for each customer, to display many orders.
What to do
When you use the Database Form Expert, building a master-detail form is much like
building a single-table form (for details, see page 21).
1 Choose Help|Database Form Expert to open the Form Expert.
2 In the first panel, specify a master-detail form that uses TTable objects.
3 In subsequent panels, specify the master table (CUSTOMER.DB), fields (use them
all), and field layout (grid).
4 Specify the detail table (ORDERS.DB), fields (all), and field layout (grid).
5 Specify fields to link the master and detail tables as shown in the following figure, then tell the expert to create the form.
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