Visual Basic 6 Business Objects
In this chapter, we returned to the CSLA. We looked at how that logical architecture can be implemented on a single machine and across multiple machines. As the number of physical tiers is increased, we can gain better distribution of the processing - increasing our flexibility and scalability with each layer. Of course, each extra layer of hardware can add communications overhead to our application.
We explored some of the business object design issues that impact user-interface developers. One of the primary goals of a business object developer is to make it easy for UI developers to work with the objects. At the same time, the business objects must protect themselves. Essentially, the business object developer must assume that the user-interface code will do something to break the objects - and the developer must take steps to prevent that from happening.
We wrapped up the chapter by looking at different techniques that we can use to save and restore object data in a database, or make objects persistent. Making objects persistent is the key to creating client/server applications using business objects. Most of an application's performance issues surround the techniques used to persist objects in a database, so it's important to choose the appropriate technique for each application.
We'll continue to explore the concepts from this chapter throughout the remainder of the book. Using the video store example from Chapter 3, we'll walk through the development of a series of applications by applying the CSLA to each typical physical model. Here's what we'll be looking at through the next few chapters:
- Chapter 5 Build the simpler objects for a Video store
- Chapter 6 Build more complex parent-child objects for a Video store
- Chapter 7 Create a UI using Visual Basic forms
- Chapter 8 Add code to our objects to save themselves to the database
- Chapter 9 Create a UI using Microsoft Excel
- Chapter 10 Using data-centric business objects over Distributed COM
- Chapter 11 Distributing objects over DCOM
- Chapter 12 Using data-centric business objects with Microsoft Transaction Server
- Chapter 13 Active Server Pages and HTML as a front end
- Chapter 14 Using an IIS Application as a front end
- Chapter 15 Create a UI using a DHTML Application
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