What Does the `= delete` Syntax Do in C Class Definitions?

The enigmatic = delete: Defining Class Functionality

In C , the = delete syntax following a function declaration holds a significant purpose. It denotes the explicit deletion of a function. This feature, introduced in C 11, provides unprecedented control over class behavior.

What = delete Accomplishes

When a function is deleted, it effectively becomes prohibited to call, i.e., it cannot be invoked on an object of the class. This approach is particularly useful when one wishes to disallow copying or assignment operations or prevent certain conversions.

For instance, in the following code snippet:

class my_class
{
    ...
    my_class(my_class const &) = delete;
    ...
};

The constructor my_class(my_class const &) is intentionally marked as deleted, precluding the creation of copy constructors.

Extending Functionality Beyond Copying and Deletion

Apart from its ability to delete functions, C also offers additional modifiers that can be appended to function declarations. These include:

• = 0: This syntax declares a pure virtual function, which must be implemented in derived classes.
• = default: This specifies that the function should use the default implementation provided by the compiler.

Customizing Class Behavior

As demonstrated, the = delete syntax and other modifiers empower programmers to tailor class functionality precisely. By deleting functions or enforcing other stipulations, class designers can effectively guide the interaction with their objects, ensuring that they behave as intended.

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