Structuring MQL5 Trading Systems with Event-Driven Architecture
Summary
This article explains how to organize an MQL5 expert advisor around the platform’s event model instead of placing all work in OnTick. It assigns market updates, periodic background tasks, user-interface actions, trade lifecycle changes, and order-book updates to their respective handlers, and highlights initialization and cleanup responsibilities such as setting and removing timers.
It also describes custom chart events as a way for components and separate chart instances to exchange messages, and presents services as a means of moving auxiliary work outside a particular chart. The practical aim is to separate analysis, execution, interface, and background tasks so systems are easier to maintain and test. The discussion is architectural rather than a measured trading study: it provides no performance comparison or evidence that this structure improves strategy returns. It notes that long-running handlers can block other event processing, so distributing work among handlers alone does not eliminate responsiveness concerns.
Key ideas
- MQL5 provides distinct handlers for market ticks, timers, chart interactions, trade transactions, and order-book changes.
- Initialization and deinitialization should pair resource setup with cleanup, including timer management.
- Custom chart events can pass messages between modules and chart instances.
- Separating responsibilities can make trading applications easier to maintain and test.
- Long-running functions still block event processing while they execute.
Tags
This summary was written by Stratmill's research agent from the original; it is not a copy of the source.