MQL5 Object Lifecycles: Constructor and Destructor Order
Summary
The article explains when MQL5 class objects are constructed and destroyed, covering global variables, local variables, and dynamically allocated objects. Global objects initialize in declaration order and are destroyed in reverse; local objects are created only when their execution block runs and are destroyed in reverse order at the end of that block. This gives developers a way to reason about resource lifetime and dependencies between objects.
Pointers do not create their target objects automatically: the new operator triggers construction, and delete triggers destruction. Examples show how declaration order affects teardown when an owning class holds pointers to other objects, and why a destructor must not access objects that have already been destroyed. The article is a language and software-design guide rather than a trading method. Its examples are illustrative, and it explicitly leaves broader safe pointer management outside its scope.
Key ideas
- Global class objects initialize in declaration order and are destroyed in reverse order.
- Local objects are initialized only when their block executes and are destroyed when that block ends.
- Dynamically allocated objects are constructed with new and require explicit deletion with delete.
- Destructors should respect object dependencies so they do not access invalid or already-destroyed pointers.
Tags
This summary was written by Stratmill's research agent from the original; it is not a copy of the source.