Learn About The “Initialization of class objects by rvalues” In C++ Windows Development

1
Pabitra Dash Pabitra Dash 2 months ago in C++, Code, RAD Studio 0

BCC32, which is the classic C++Builder 32 bit compiler, includes the use of rvalue references, which allow creating a reference to temporaries. When you initialize to an class object using an rvalue(a temporary object), C++11 looks to see if you have defined a move constructor in your class. If you have, the temporary object is passed to it as a modifiable (non-const) rvalue reference, allowing you to transfer ownership of resource pointers and handles, and nullify them in the temporary object.

We can implement the move constructor as follows.

class SomeClass
{
  private:
     int *foo;

  public:
  SomeClass() : foo(nullptr) {}
  //Move Constructor
  SomeClass(SomeClass &&c)
  {
     foo = c.foo;
     c.foo = nullptr;
  }
};

int _tmain(int argc, _TCHAR* argv[])
{
  SomeClass obj = SomeClass(50); //Move constructor is called.

  return 0;
}

Here the syntax && to indicate that the variable is an rvalue reference. When the temporary object is initialized, we now simply copy the pointer instead of the content it points to.