New article OOP in MQL5 by Example: Processing Warning and Error Codes is published:
The article describes an example of creating a class for working with the trade server return codes and all the errors that occur during the MQL-program run. Read the article, and you will learn how to work with classes and objects in MQL5. At the same time, this is a convenient tool for handling errors; and you can further change this tool according to your specific needs.
Before we start developing, let's get acquainted with some features of the OOP, which will be used in this article. Of course, we will use structures and classes. These are the basics of object oriented languages. What is the structure, what is the class and how do they differ?
A structure is a construction that allows containing a set of variables and functions of different types (except void).
as well as the structure is a set of data fields. But a class is a more
complicated and "Flexible" construction. Classes are the basic concept
of the OOP.