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Introduction When working with object-oriented programming (OOP), the concept of member variables and their visibility is fundamental. Xbase++ follows these principles, offering various visibility levels for member variables in classes. This article intends to explore these concepts in the context of Xbase++, targeting coding practitioners in business application development. Our goal is to clarify when to use different visibility levels for member variables, enhancing your software design...

Xbase++ developers often use ISAM (Indexed Sequential Access Method) for data management because of its efficiency and straightforward approach to handling database operations. Moving to PostgreSQL, a robust SQL database, offers enhanced capabilities but requires an understanding of new concepts, one of which is the use of remote filters. In the context of PostgreSQL's ISAM emulation, remote filters play a fundamental role in ISAM-based data query optimization and performance. The basic...

Background Xbase++ allows seamless integration with SQL backends like PostgreSQL using the DacSession() object. When working with SQL databases, enforcing data integrity through application logic alone is not always sufficient. Native SQL constraints (such as CHECK, UNIQUE, or FOREIGN KEY) ensure that the database maintains consistent and valid data, even when the application logic fails or behaves unexpectedly. Example Code Below is a code snippet that updates the totalsales field in the...

The re-implementation of existing legacy software systems often faces significant challenges, and understanding these can illuminate why such projects frequently fail. This little write-up is far from complete but tries to create awareness regarding these important and very often underrated challenges. We will conclude with a comparison of migration strategies with their monetary and risk advantages. Challenges in Re-Implementation of Legacy Systems Understanding Original System...

Background As you may have already realized, a PostgreSQL server or any SQL server in general is a "relatively" complicated story. The reason for that is basically that the server with the planner tries to replace you as a human. In ISAM you have the data model in mind, also the requirements of the system regarding which data is needed when. In the code you write all this down and have a highly specialized but also high performance system - in a ideal world of course. With a SQL Server...