RAII: Initializing data member in const method
c++, const-correctness, lazy-evaluation
Solution
This is not RAII. In RAII you would initialize it in the constructor, which would solve your problems.
So, what you are using here is `Lazy`. Be it lazy initialization or lazy computation.
If you don't use `mutable`, you are in for a world of hurt.
Of course you could use a `const_cast`, but what if someone does:
static const MyClass Examplar;
And the compiler decides it is a good candidate for Read-Only memory ? Well, in this case the effects of the `const_cast` are undefined. At best, nothing happens.
If you still wish to pursue the `const_cast` route, do it as `R Samuel Klatchko` do.
If you thought over and think there is likely a better alternative, you can decide to wrap your variable. If it was in class of its own, with only 3 methods: `get`, `set` and `load_from_database`, then you would not worry about it being `mutable`.
Problem
In RAII, resources are not initialized until they are accessed. However, many access methods are declared constant. I need to call a `mutable` (non-const) function to initialize a data member. Example: Loading from a data base ``` struct MyClass { int get_value(void) const; private: void load_from_database(void); // Loads the data member from database. int m_value; }; int MyClass :: get_value(void) const { static bool value_initialized(false); if (!value_initialized) { // The compiler complains about this call because // the method is non-const and called from a const // method. load_from_database(); } return m_value; } ``` My primitive solution is to declare the data member as `mutable`. I would rather not do this, because it suggests that other methods can change the member. How would I cast the `load_from_database()` statement to get rid of the compiler errors?