Creating a DataWindow object

This section describes how to create a DataWindow object by calling the Create method in an application.

DataWindow painter You should use the techniques described here for creating a DataWindow from syntax only if you cannot accomplish what you need to in the DataWindow painter. The usual way of creating DataWindow objects is to use the DataWindow painter.

To learn about creating DataWindow objects in the DataWindow painter, see the PowerBuilder Users Guide.

You use the Create method to create a DataWindow object dynamically during execution. Create generates a DataWindow object using source code that you specify. It replaces the DataWindow object currently in the specified DataWindow control with the new DataWindow object.

Resetting the transaction object The Create method destroys the association between the DataWindow control and the transaction object. As a result, you need to reset the control’s transaction object by calling the SetTransObject or SetTrans method after you call Create.

Web ActiveX If you used a connection technique that did not require you to call the SetTransObject or SetTrans method, you do not need to call it after Create either.

To learn how to associate a DataWindow control with a transaction object, see Chapter 2, “Using DataWindow Objects.”

Specifying the DataWindow object syntax

There are several ways to specify or generate the syntax required for the Create method. Not all the techniques are available in all environments.

In PowerBuilder, you can:

Use the SyntaxFromSQL method of the transaction object
Use the LibraryExport PowerScript function

In all environments, you can:

Use the DataWindow.Syntax property of the DataWindow object
Create the syntax yourself

Using SyntaxFromSQL You are likely to use SyntaxFromSQL to create the syntax for most dynamic DataWindow objects. If you use SyntaxFromSQL, all you have to do is provide the SELECT statement and the presentation style.

In PowerBuilder, SyntaxFromSQL is a method of the transaction object. The transaction object must be connected when you call the method.

Setting USERID for native drivers In PowerBuilder, table names are automatically qualified with the owner’s name if you are using a native driver. To obtain the same results in an application, you must set the USERID property in the transaction object so that the table name is properly qualified and extended attributes can be looked up.

SyntaxFromSQL has three required arguments:

A string containing the SELECT statement for the DataWindow object
A string identifying the presentation style and other settings
The name of a string you want to fill with any error messages that might result

SyntaxFromSQL returns the complete syntax for a DataWindow object that is built using the specified SELECT statement.

Using SyntaxFromSQL with Adaptive Server Enterprise If your DBMS is Adaptive Server Enterprise and you call SyntaxFromSQL, PowerBuilder must determine whether the tables are updatable through a unique index. This is possible only if you set AutoCommit to TRUE before calling SyntaxFromSQL, as shown below:

sqlca.autocommit=TRUE

sqlca.syntaxfromsql (sqlstmt, presentation, err)

sqlca.autocommit=FALSE

Using LibraryExport in PowerBuilder You can use the LibraryExport PowerScript function to export the syntax for a DataWindow object and store the syntax in a string.

You can then use the exported syntax (or a modification of the syntax) in Create to create a DataWindow object.

Using the DataWindow.Syntax property You can obtain the source code of an existing DataWindow object to use as a model or for making minor changes to the syntax. Many values in the source code syntax correspond to properties of the DataWindow object.

This JavaScript example gets the syntax of the DataWindow object in the DataWindow control, dw_1, and displays it in the text box control, textb_dw_syntax :

var dwSyntax;

dwSyntax = dw_1.Describe("datawindow.syntax");
textb_dw_syntax.value = dwSyntax;

Creating the syntax yourself You need to create the syntax yourself to use some of the advanced dynamic DataWindow features, such as creating a group break.

The DataWindow source code syntax that you need to supply to the Create method can be very complex. To see examples of DataWindow object syntax, go to the Library painter and export a DataWindow object to a text file, then view the file in a text editor.

For more information on Create and Describe methods as well as DataWindow object properties and syntax, see the DataWindow Reference.