operatorMoveOnly

operatorMoveOnly is a C++20 feature that allows a class to declare that its objects can only be moved, not copied. This is achieved by marking all copy constructor and copy assignment operator overloads as deleted. This signifies that the object's state is not intended to be duplicated, and operations that would involve copying are explicitly disallowed.

When a class has operatorMoveOnly semantics, attempting to copy an object of that class will result in a compilation error. However, moving such an object is still permitted. A move operation transfers ownership of resources from one object to another, typically leaving the source object in a valid but unspecified state. This is distinct from copying, which creates an independent duplicate.

The primary use case for operatorMoveOnly is for resource management classes where duplication is either impossible, undesirable, or inefficient. Examples include file handles, network sockets, unique pointers, and other objects that manage unique system resources. By preventing copies, operatorMoveOnly helps enforce the "single ownership" principle and avoids potential issues like double-freeing resources or maintaining inconsistent states.

To implement operatorMoveOnly, developers must explicitly delete the copy constructor and copy assignment operator. For instance, in a class definition, one would write:

class MyClass {

public:

MyClass(MyClass&&) = default; // Move constructor (optional, can be defaulted or custom)

MyClass& operator=(MyClass&&) = default; // Move assignment operator (optional, can be defaulted or custom)

MyClass(const MyClass&) = delete; // Delete copy constructor

MyClass& operator=(const MyClass&) = delete; // Delete copy assignment operator

// Other members...

};

This explicitly disallows copying while allowing moving, thus establishing the operatorMoveOnly behavior for instances of MyClass.