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++17 you can use std::optional to check if a variable is initialized:

#include 
#include   // needed only for std::cout

int main() {
    std::optional variable;

    if (!variable) {
        std::cout << "variable is NOT initialized\n";
    }

    variable = 3;

    if (variable) {
        std::cout << "variable IS initialized and is set to " << *variable << '\n';
    }

    return 0;
}

This will produce the output:

variable is NOT initialized
variable IS initialized and is set to 3

---

To use std::optional in the code snipped you provided, you'll have to include the standard library header and add std::optional<...> to the respective variable declarations:

#include 

class MyClass
{
    void SomeMethod();

    std::optional mCharacter;
    std::optional mDecimal;
};

void MyClass::SomeMethod()
{
    if ( mCharacter )
    {
        std::cout << *mCharacter;  // do something with mCharacter.
    }

    if ( ! mDecimal )
    {
        mDecimal = 3.14159;  // define mDecimal.
    }
}