Pattern name for create in constructor, delete in destructor (C++)

Question

Traditionally, in C++, you would create any dependencies in the constructor and delete them in the destructor.

class A
{
 public:
    A() { m_b = new B(); }
         


        

Answer 1

The answer to your question is RAII (Resource Acquisition Is Initialization).

But your example is dangerous:

Solution 1 use a smart pointer:

class A
{
  public:
     A(): m_b(new B) {}
  private:
     boost::shared_ptr<B> m_b;
};

Solution 2: Remember the rule of 4:
If your class contains an "Owned RAW pointer" then you need to override all the compiler generated methods.

class A
{
  public:
     A():              m_b(new B)           {}
     A(A const& copy): m_b(new B(copy.m_b)) {}
     A& operator=(A const& copy)
     {
         A  tmp(copy);
         swap(tmp);
         return *this;
     }
    ~A()
     {
         delete m_b;
     }
     void swap(A& dst) throw ()
     {
         using std::swap;
         swap(m_b, dst.m_b);
     }
  private:
     B* m_b;
};

I use the term "Owned RAW Pointer" above as it is the simplest example. But RAII is applicable to all resources and when your object contains a resource that you need to manage ('Owned RAW Poiner', DB Handle etc).

Answer 2

RAII - Resource Acquisition Is Initialization

Answer 3

This technique is best known as RAII - Resource Allocation Is Initialization. It has its own tag on this site.

Alternative. more intuitive names have been suggested, in particular:

• UDSTMR - Using Destructor Semantics To Manage Resources.
• UTSTTC - Using The Stack To Trigger Cleanup.
• LECLEOEIGU - Lifetime Equals Class Lifetime Or Else It Gets Ugly (the original suggestion, LECCLEOEIGU - Lifetime Equals C++ Class Lifetime Or Else It Gets Ugly, includes the language name, which I prefer to remove in this answer because the language is known).