Advanced PowerBuilder

Automation

Automation refers to the ability of an application to define a set of properties and commands and make them accessible to other applications to enable programmability. OLE provides a mechanism through which this access is achieved. Automation increases application interoperability without the need for human intervention.

The main purpose of this can be best described in an example. Let's say that you have some data in a database you would like to perform a regression analysis. Typically, the database developer would have to create a function or sub-routine that contains the regression analysis formula and then pass the data to the function. The development of this function could take a considerable amount of time. In fact, why create a routine when spreadsheets do regression analysis quite well? So, the better approach would be to "pass" the data to the spreadsheet program, "instruct" the spreadsheet program to perform the regression analysis on the data, and "pass" back the results. This allows a macro developer to open up entirely whole new worlds. In fact, you could even start to consider a spreadsheet program as one large compilation of subroutines and functions that are easily callable and accessible.

This was previously achieved through a mechanism called Dynamic Data Exchange or DDE. DDE would give application macro developers the ability to control one application from another, but the methods to achieve this were not trivial. DDE required that a significant amount of time be devoted to error-handling and only a limited amount of data could be automatically passed from one application to another at one time. Consider the example of performing a regression analysis on data in a database. The following steps quickly map out what commands would be necessary if DDE calls were made:

Establish a connection from the controlling application (source) to the application (destination) that will be controlled.

• Test to make sure that the destination application can receive the commands and is not busy.
• From the source application, tell the destination application what is trying to be accomplished.
• Test to make sure the destination application can handle what is trying to be accomplished.
• Take one data point at a time from the source application and pass it to the destination.
• Test each data point to ensure that the destination received it and that the connection is still live.
• Once all the data points have been sent to the destination, instruct the destination to perform the regression analysis on the entire data set (this is even another command).
• Prepare the source to now receive the result of the regression analysis and pass the result from the destination to the source.
• Test to ensure that the source received the result.
• Close the connection.
• This example appears quite simplistic, but from a DDE programming standpoint this would likely take around 60 lines of code.

With OLE and OLE Automation, the process to achieve this is significantly easier. Applications written to support OLE expose properties and commands that can be controlled from other applications. The public exposure of these properties and commands allows one application to contain code that manipulates another application. It also allows developers to create new applications that can interact with existing applications.

• Using OLE automation in the above example, we will see how the same results can be achieved with minimum effort:
• Establish a connection from the controlling application (source) to the application (destination) that will be controlled.
• Define the entire data set in the source as an object and pass the object to the destination.
• Instruct the destination to perform the regression analysis on the object.
• Instruct the destination application to return the result of the regression analysis to the source application.