Return by value is the simplest and safest return type to use. When a value is returned by value, a copy of that value is returned to the caller. As with pass by value, you can return by value literals (eg. 5), variables (eg. x), or expressions (eg. x+1), which makes return by value very flexible.
Advantage of return by value is that you can return variables (or expressions) that involve local variables declared within the function. Because the variables are evaluated before the function goes out of scope, and a copy of the value is returned to the caller, there are no problems when the variable goes out of scope at the end of the function.
int DoubleValue(int nX)
{
int nValue = nX * 2;
return nValue; // A copy of nValue will be returned here
}
Return by value is the most appropriate when returning variables that were declared inside the function, or for returning function arguments that were passed by value. However, like pass by value, return by value is slow for structs and large classes.
Conclusion
ReplyDeleteMost of the time, return by value will be sufficient for your needs. It’s also the most flexible and safest way to return information to the caller. However, return by reference or address can also be useful, particularly when working with dynamically allocated classes or structs. When using return by reference or address, make sure you are not returning a reference to, or the address of, a variable that will go out of scope when the function returns!