When a constructor throws an exception, how can I prevent the object from being created?
In the example below, I create a Month() class, for which legal values of the int month_
property are in the range of 1 to 12. I instatiate December, or dec
, with integer value 13. The exception is thrown, as it should be, but the object is still created. The destructor is then called.
How do I abort creation of a class instance upon a thrown exception?
OUTPUT
-- Month() constructor called for value: 2
-- Month() constructor called for value: 6
-- Month() constructor called for value: 13
EXCEPTION: Month out of range
2
6
13
-- ~Month() destructor called.
-- ~Month() destructor called.
-- ~Month() destructor called.
Press any key to exit
Minimal, complete, and verifiable example
#include <iostream>
#include <string>
class Month {
public:
Month(int month) {
std::cout << "-- Month() constructor called for value: " << month << std::endl;
try {
if ((month < 0) || month > 12) throw 100;
} catch(int e) {
if (e == 100) std::cout << "EXCEPTION: Month out of range" << std::endl;
}
month_ = month;
}
~Month() {
std::cout << "-- ~Month() destructor called." << std::endl;
}
int getMonth()const { return month_; }
private:
int month_;
};
int makeMonths() {
Month feb(2), jun(6), dec(13);
std::cout << feb.getMonth() << std::endl;
std::cout << jun.getMonth() << std::endl;
std::cout << dec.getMonth() << std::endl;
return 0;
}
int main() {
makeMonths();
std::cout << "Press any key to exit"; std::cin.get();
return 0;
}
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