GAMBAS BOOK 3.19.3

A DataSource is a container control that provides data from a database (recursively) to all controls in this container. The database is defined via the Connection property.

You can use the Table and Filter properties to specify which database data should actually be available, for example for display:

    DataSource1.Connection = DBCS.DBConnection
'-- Filtering   --------------------------------------------------------------------
    DataSource1.Table = "contacts"
    DataSource1.Filter = "id > 4 AND wohnort <> 'Berlin' AND wohnort NOT LIKE 'G%'"
'-----------------------------------------------------------------------------------
    DataSource1.Sort = "wohnort"

The DataSource class has the following properties:

Table 22.5.3.1.1 : Properties of the DataSource class

The DataSource class has these special methods:

Table 22.5.3.2.1 : Methods of the DataSource class

The DataSource class only has three special events:

• BeforeSave ( Data As Result ): This event is triggered before the values from the DataControls used are saved to the DB table, provided there is a connection to it. The data is saved in the result object (Result data type). Use the event to change data before it is written to the database table.
• BeforeDelete ( Keys As Variant[] ): This event is triggered before a record is deleted. Keys is an array with the values of the primary key that identifies the data record to be deleted. You can cancel the deletion by stopping the event.
• Change ( ): The event is triggered when the current data record has been changed and all controls in the container have been updated.

Example 1 - Event: BeforeSave ( Data As Result )

The selected data set can still be changed before saving. The two potential changes shown here are only intended to demonstrate the procedure:

Public Sub DataSource1_BeforeSave(Data As Result)
 
'-- If the date is missing, the current date is saved.
    If Data["date"] = Null Then Data["date"] = Now()
 
'-- If the image is missing, you will be prompted to save an image.
    If Data["picture"].Length = 0 Then 
       Message.Info("Action:<br>Insert new image.")
    Else
       If Message.Question("Do you want to change the current image?", "Yes", "No") = 1 Then
          Print "Action: Change current image."
       Else 
          Print "Action: No change current image."
          Stop Event
       Endif
    Endif
 
  Catch
    Message.Error(Error.Text & gb.NewLine & Error.Where)
 
End

Example 2 - Event: BeforeDelete ( Keys As Variant[ ] )

The focus here is on the confirmation prompt as to whether the selected data record should actually be deleted:

Public Sub DataSource1_BeforeDelete(Keys As Variant[])
 
    Dim vElement As Variant
    Dim sQuestion As String
 
'-- For Each vElement In Keys
'--     Print vElement
'-- Next
 
    sQuestion = Subst("&1 `&2` &3", ("Should the record with the ID"), Keys[0], ("be deleted?"))  
    If Message.Question(sQuestion, "Yes", "No") = 2 Then
       Stop Event
    Endif  
End

Example 3 - Deleting the current data record from the DB table:

Dim bFlag As Boolean
If DataSource1.Remove() = False Then Print "THE DELETION OF THE DATA SET WAS SUCCESSFUL!"

Example 4 - Setting the DB table field to be sorted by:

DataSource1.Sort = "PLZ"

Example 5 - Setting a filter:

    MDataBase.ConnectDB("mysql", "localhost", "3606", "root", "sql", "Kontakte", "kontakte")
    DataSource1.Connection = MDataBase.hConnection
    DataSource1.Table = "kontakte"
'-- DataSource1.Filter = "Wohnort <> 'Leipzig' AND Wohnort NOT LIKE 'G%'" ' "Wohnort <> \"Leipzig\""
    DataSource1.Filter = "" '-- Standard-Filter

Note: In MySQL, the patterns are not case-sensitive by default.

Additions

In commit https://gitlab.com/gambas/gambas/commit/6902893dd50e6480a63aa2268207241aea021f3 the new property “IgnoreParent” has been added to the DataSource control. If this property is set to TRUE, the DataSource will not filter its content with the primary keys of its parent DataSources. It will behave as if it were a root DataSource.