MQL5 Structures, Unions, Classes, Function Types, and Include Files
Summary
This beginner programming tutorial explains how MQL5 combines simple values into structures, overlays different interpretations of data with unions, introduces classes and function types, and brings external source files into a program with include directives. Examples use trade-related records such as order signals and execution times to show field access, nested structures, and initialization. It also describes alignment and field offsets for structures used with external libraries.
The article emphasizes that organizing related data and code into types and modules can make programs easier to maintain. Its examples are instructional rather than trading research: it presents no strategy, performance evidence, or tests of trading outcomes. Some low-level topics, especially structure copying, casting, and union use, have constraints that the article only summarizes; readers working with DLLs or relying on precise memory layouts should consult the MQL5 reference.
Key ideas
- Structures group related fields, including fields that are themselves structures.
- Union members share storage, allowing the same memory to be interpreted through different types.
- Brace initialization assigns values in field order, and omitted trailing fields receive zero values.
- Packing and field offsets matter when matching MQL5 structures to external interfaces.
- Include directives split related program components across files to support modular development.
Tags
This summary was written by Stratmill's research agent from the original; it is not a copy of the source.