Question

When I try to compile the following function I get the error.

string& foo(){
return "Hello World";
}


Error:
1   IntelliSense: a reference of type "std::string &" (not const-qualified) cannot be initialized with a value of type "const char [12]"

Answer 1

There are two problems with your code. First, "Hello World!" is a
char const[13], not an std::string. So the compiler has to
(implicitly) convert it to an std::string. The result of a
conversion is a temporary (rvalue in C++-speak), and you cannot
initialize a reference to a non-const with a temporary. The second is
that even if you could (or you declared the function to return a
reference to const), you’re returning a reference to something which
will immediately go out of scope (and thus be destructed); any use of
the resulting reference will result in undefined behavior.

The real question is: why the reference? Unless you’re actually
referring to something in an object with a longer lifetime, with the
intent that the client code modify it (usually not a good idea, but
there are notable exceptions, like operator[] of a vector), you should
return by value.