Static members - MQL4

Static Members of a Class/Structure

Declared using the static storage class modifier.

Shared by all instances of a class; stored in one place.

Contrast with non-static members, which are created per object.

Allows class-specific data not tied to an instance to exist within the class scope.

Accessed via class_name::variable.

Context resolution operator :: is used for access.

Optional within class methods.

Must be explicitly initialized in the global scope.

Initialization sequence follows declaration order.

**Example (CParser):**

class CParser { public: static int s_words; static int s_symbols; };
int CParser::s_words = 0;
int CParser::s_symbols = 0;

Can be declared with the const keyword.

Must be initialized globally with the const keyword.

**Example (CStack):**

class CStack { private: static const int s_max_length; };
const int CStack::s_max_length = 1000;

Refers to the current class instance.

Available only in non-static methods.

Static functions cannot access non-static members or use this.

Declared using the static modifier before the return type within the class.

Can only access static members/methods of the class.

**Example (CStack::Capacity):**

class CStack { public: static int Capacity(); };
int CStack::Capacity(void) { return(s_max_length); }

**Accessing Static Methods:**

object.static_method()

ClassName::static_method()

Applies to non-static member functions.

Indicates the function does not modify implicit class members.

Ensures compiler checks for consistency.

const modifier placed after the argument list in declaration and definition.

Static functions cannot be declared const as they don't operate on an instance.

**Example (CRectangle::Square):**

class CRectangle { public: double Square(void) const; };
double CRectangle::Square(void) const { return(Square(m_width,m_height)); }

Compilers may optimize const objects by placing them in read-only memory.