Resource Acquisition is Initialization

Language Note #2:

The C++ language uses scope based deallocation. The destructor of any class instance is called when the thread of execution leaves the scope in which the instance was declared.

When the compiler encounters an opening brace, "{", in an executable statement, it generates code to create a stack frame, defining the beginning of a new scope. When compilation encounters a closing brace, "}", in an executable statement, the stack frame is deallocated, and execution will leave that scope. Every time a stack frame is deallocated, destructors are called on any instances of classes or structs created in that frame.

If you imagine a virtual machine that executes source code, then you enter a scope when execution encounters an opening brace and leave the scope when it encounters the matching closing brace. So objects constructed inside the braces are destroyed when execution crosses the closing brace.

This is a very powerful way to manage program resources. We acquire resources in the constructor of a class and deallocate them in its destructor. Developers using your class don't have to remember to do any clean up. The instance does that for itself automatically as it goes out of scope.

Conclusions for: Resource Acquisition is Initialization

Well designed value types created with C++ classes use scope based management of their resources.

Any resources acquired by the class during its construction or invocation of other member functions is returned by its destructor.
C++ conspires to automatically destroy all instances of types declared in any scope when the thread of execution leaves that scope.
That means that the C++ language provides you the means to make your classes entirely responsible for managing their own resources. Users of the class don't have to know anything or remember anything to support that. They simply declare instances of the class in the scope where they need it and allocation and deallocation happen automatically.
If users need more persistant life time, they get a pointer to an instance of your class on the heap by using the new operator; and when they have finished with the object, destroy it by calling delete on the pointer.

CSE687 - Object Oriented Design

Language Note #2
Resource Acquisition is Initialization (RAII)

Language Note #2:

Conclusions for: Resource Acquisition is Initialization

CSE687 - Object Oriented Design

Language Note #2Resource Acquisition is Initialization (RAII)

Language Note #2:

Conclusions for: Resource Acquisition is Initialization

Language Note #2
Resource Acquisition is Initialization (RAII)