Checking if a variable is initialized

Question

Seems like this would be a duplicate, but maybe it is just so obvious it hasn\'t been asked...

Is this the proper way of checking if a variable (not pointer) is init

Answer 1

With C++-11 or Boost libs you could consider storing the variable using smart pointers. Consider this MVE where toString() behaviour depends on bar being initialized or not:

#include 
#include 

class Foo {

private:
    std::shared_ptr bar;

public:
    Foo() {}
    void setBar(int bar) {
        this->bar = std::make_shared(bar);
    }
    std::string toString() const {
        std::ostringstream ss;
        if (bar)           // bar was set
            ss << *bar;
        else               // bar was never set
            ss << "unset";
        return ss.str();
    }
};

Using this code

Foo f;
std::cout << f.toString() << std::endl;
f.setBar(42);
std::cout << f.toString() << std::endl;

produces the output

unset
42