Is there any way you can have a constructor fail so that the class isn't created? i.e.
Code:Socket::Socket(char *addr, int port) { if (connect(addr, port) == FAIL) { fail; } }Code:int main() { Socket *sock = new Socket("google.com", 80); if (sock == NULL) { printf("It didn't work\n"); return 0; } }
You could throw an exception.
Also in your example code new won't return a NULL if it fails. It'll throw an exception.
Another option is to just put the object into a failed state.
Or make an empty constructor and use a Create() member function which returns a bool.
throwing an exception is a easy way
or you can use safe_bool
Code:class A { struct dummy{ void non_null(){} }; typedef void (dummy::*safe_bool)(); bool init(); public: A():is_failed_(false) { is_failed_ = init(); } bool failed() const { return is_failed_; } operator safe_bool() const { return (this->failed())? 0 : &dummy::non_null; } private: bool is_failed_; }; int main() { A a; if(a) cout<<"yes"<<endl; else cout<<"no"<<endl; }
Nana C++ Library is a GUI framework that designed to be C++ style, cross-platform and easy-to-use.
oh cause i picked up the topic...
in case that construction fails how can the memory be cleaned up?
afaik the memory remains - especially when creation of an member fails it cannot free memory of the "parent" object.
i think i read something that the member new and delete functions are used to clean such mess up again...
signature under construction
