Polymorphism in MQL4 allows different classes, linked by inheritance, to exhibit distinct behaviors when a common function is invoked. This is achieved through:
**Virtual Functions:** Base classes can declare virtual functions that derived classes can redefine to implement specific behaviors. For example, a CShape base class with a virtual double GetArea() function can be extended by CCircle and CSquare classes, each providing its own implementation of GetArea().
**Function Overloading:** A class can define multiple functions with the same name but different parameter lists (types and/or number of arguments). This allows for varied function implementations within a single class.
**Dynamic Object Management:** Polymorphism often involves working with objects of unknown types at compile time. This necessitates:
CShape *shapes[5]) to refer to objects of base or derived classes.new operator (e.g., new CCircle()).delete operator (e.g., delete shapes[i]).CheckPointer() to ensure it's POINTER_DYNAMIC. Attempting to delete pointers of other types (e.g., POINTER_INVALID, POINTER_NULL) will result in an error.**Example Scenario:**
CShape base class with m_type, m_xpos, m_ypos members and a virtual GetArea() function.CCircle (with m_radius) and CSquare (with m_square_side), each overriding GetArea().CShape pointers (CShape *shapes[5]) is used to store pointers to dynamically created CCircle and CSquare objects.new and assigned to array elements. Unused elements are set to NULL.GetType() and GetArea() on each valid object pointer. The correct GetArea() implementation is invoked based on the object's actual type at runtime.delete all dynamically allocated objects, ensuring proper memory management.