string receiveFromServer();
this function returns a string that was received from some server. If there was an error along the way (including protocol), i want to return a NULL string. However, this doesn't work in c++ (unlike java). i tried:
string response = receiveFromServer();
if (response==NULL) {
cerr << "error recive response\n";
}
but its not legal. Since an empty string is also legal to return, what can i return that will indicate the error?
thank you!
You can throw an exception to indicate an error.
try {
std::string response = receiveFromServer();
} catch(std::runtime_error & e) {
std::cerr << e.what();
}
Then you would need a throw std::runtime_error("Error receive response") somewhere in receiveFromServer().
It is often considered good practice (though some might disagree) to create your own exception-classes that derive from std::runtime_error to enable clients to catch your errors specifically.
You can either throw an exception (better way), or return boost::optional< string >, but then you have to check if the return value is valid (this is actually worse).
boost::optional, you can also use std::pair<string, bool>.
optional is the way to go.NULL has only a meaning when using pointers. In java strings are pointers so you can do that.
In C++, if you return an std::string, it must exist. So you have some possibilites
Maybe you should try to handle with exceptions
try
{
string response = receiveFromServer();
}
catch (...)
{
cerr << "error recive response\n";
}
If you want to return an empty string you could also use the function
string::empty() to test if it is empty
