I'm having a hard time figuring out how to return a non-const
reference to an element in a std::vector
from a const member function. A simple example of what I'm going for is,
template<class T>
class MyClass
{
public:
MyClass : myVec(3)
{
}
T& x() const
{
return *(myVec.data())[0]
}
std::vector<T> myVec;
}
The behavior I'm going for is that I'd like to be able to do things like the following,
MyClass obj<double>;
obj.x() = 3.3;
assert(obj.x()==3.3)
Eigen gives the same type of behavior, but I've not been able to figure out how to get it to work.
You could use const_cast
, and it'll do the work here, (according to the usage posted). But you won't need it for this case (and for most cases).
You could (and should) add non-const member function overloading for it. Then const member function returns reference to const, non-const member function returns reference to non-const. The appropriate one will be invoked via overload resolution.
const T& x() const
{
return myVec[0];
}
T& x()
{
return myVec[0];
}