destructor

A destructor is a special member function that is automatically invoked when an object's lifetime ends. Its primary purpose is to release resources that the object acquired during its lifetime, such as dynamically allocated memory, file handles, or network connections.

In languages with deterministic destruction like C++, the destructor is defined as ~ClassName() and is called when an object goes out of scope or is explicitly deleted. Destructors typically do not take arguments or return values and may be declared virtual to enable correct cleanup through base-class pointers.

In garbage-collected languages, destruction is often non-deterministic. For example, C# uses a finalizer (~ClassName) that is invoked by the garbage collector at an unspecified time; for deterministic cleanup, the IDisposable pattern and the using statement are preferred. Java does not have a traditional destructor; finalize() exists but is deprecated in favor of explicit resource management via try-with-resources and AutoCloseable.

Python provides a destructor method named __del__, but its invocation depends on the interpreter's lifecycle and can be delayed or skipped in cycles. For reliable resource management, Python programmers typically use context managers with the with statement or explicit close methods. Rust uses the Drop trait to deterministically release resources when a value goes out of scope.

In summary, destructors are mechanisms that run at object destruction to reclaim resources and maintain invariants, with implementations and guarantees varying by language.