在Effective C ++ Item 3中，为什么要使用static_cast <const TextBlock&> （* this）而不是static_cast <const TextBlock> （*这个）？

Question

I'm reading Scott Meyers's Effective C++ 3rd.
In item 3:

Use const whenever possible. In order to use const member function operator[],non-const member function operator[] has to do 2 cast operations:

 const_cast<char&>( static_cast<const TextBlock&>(*this) [position] ) 

Why does Scott Meyers use static_cast<const TextBlock&>(*this) instead of static_cast<const TextBlock>(*this) ?

Answer 1

static_cast<const TextBlock>(*this) will create a temporary object, which is copied from *this . And then operator[] will be invoked on it, and the returned char& will be dangled when go out of the non-const member function operator[] . Note that dereference on it leads to UB.