Database forms
Contents
Overview
With HBasic you can edit the contents of a database table
- in the table editor window started from the IDE
- by writing HBasic source code that will read and write the contents
of a table
- by connecting widgets to database columns within a GUI form.
This document will describe how to connect database columns within a
form to lineedit widgets. We will call this special forms
database form
. You may create a new database form with the
database form wizard
or by inserting the needed components into an existing form.
When you have created a database form you can display and edit
values from a selected table within lineedit components within the form.
Every database forms needs a dbcursor widget which shows the buttons to
select the current database row, create a new database row or delete the
current row. You can move to the first, previous next or last database
row within the table that has been connected to dbcursor component. With
the other two buttons you can insert a new row into the table or delete
the current row from the table.
[
画像:database_form]
Prerequisites
Before you can connect to database columns you have to
- prepare HBasic for database connections
- connect a database to your project (used to select a table)
- include the hbasic_dbaccess package
The database form wizard
To create a new database with the wizard click on the
New
button in the menu or toolbar. This pops up a new dialog where you can select
the type of the new structure that you want to create. Click on the
DB-Form
wizard icon to start the wizard. In the DB-Form wizard you can see a
list of tables for the current project database. If the list is empty check
your database connection parameter and if your database is online.
Select one of the tables from this list and click OK to start the generation
of the new database form. The wizard will create a new form in your project
with a db_cursor widget and a pair of a Label widget and a LineEdit
widget for each column in the table. The text of the Label widget will display
the name of the column and the LineEdit widget will be connected to a column
of the database table through the db_cursor widget.
This form is ready to be used for editing database entries of the base-table
of the DB_CURSOR widget. Since this will not be the first form in
your project you have to call the form.load() method within another form
to start this form. You may for example set up a button
button1 in
your initial form and write a handler for the clicked event with the following
code:
' load+open another form at runtime.
Sub button1_clicked()
form2.load()
End Sub
For this example we assume that the name of the new created database form
is form2.
Create a new database form without the
wizard
If you want to set up a database form on your own start executing the following
steps:
Open a new GUI form (click on new button and select the form icon).
Load the hbasic_dbaccess package (package editor) and reate a component
of type db_cursor in your form. This component has a property which is called
DB_TABLE of type string. Set the value of this property to the name
of the database table which you want to use.
For each column that should be visible in your form create
a lineedit widget from the hbasic_stdgui package. This components has
a property which is named
DBCOLUMN. Insert the name of the database
column that should be displayed in this lineedit component into this
property.
If you now start the program the form should display the values
of the database columns within your components. You can see an example
image of a running data form at the top of this document. In the directory
/usr/local/hbasic/code_examples you may find an example program with
the name ex_db_form.bas which defines a database form for the table tab1
of the hbasic example database.
