Silly C++ reference question

Question

I do not know how to call a function with a reference in it :( It is a silly noob question I know.

The header is let's call it ref.h has a function in it that is:

virtual int funcName (Bike &biker, BikeArray &bikearray, int x, int y .... )

Within ref.h there is another header that is called Bike.h.

How do I call funcName from my main.cpp (obv. I included Bike.h and ref.h

I have called other functions from ref.h in my program, but the other functions did not have references to Bike in them, just variables... How do I declare everything?

What I have so far:

ref *ref;
Bike bike;
BikeArray bikearray;
int x, y;

ref = ref::createinstace(configFile);

ref->funcName(bike, bikearray, x,y);

ref->funcName should return results based on the configFile i passed. I have done this earlier with another function in ref.h, but that function only had int's and doubles... no objects to Bike ...

... and I get the Error "no matching function for call ref::funcName(Bike&, BikeArray&, int&, int&)

Sorry, I know this is a novice question!

Answer 1

You call the function the same way regardless of whether its arguments are passed by value or by reference.

Bike foo;
BikeArray bar;
funcName(foo, bar);

Answer 2

Pass it values not pointers.

Bike biker;
funcName(biker, ...);

Answer 3

funcName is virtual so must be a class member function. You therefore need to have a reference or pointer to the class that it is a member of first.

It would have been enough for Bike to be forwardly declared but presumably Bike.h contains the class definition for Bike. BikeArray might be a class or a typedef, for example

typedef std::vector<Bike> BikeArray;

To call funcName you would then call it using . or -> on the class reference or pointer you have, then use an instance of Bike and an instance of BikeArray to be written into, plus whatever other parameters it requires.

Answer 4

You pass objects per reference as you would pass them per copy:

someObj.funcName(myBiker, myBikeArray, 42, ...);

Note that, if a function takes arguments per non-const reference, this indicates that the function might change them. (See here for more on that.)

Also, you cannot pass rvalues (temporary objects) as non-const arguments. That means that, if you have a function that returns a biker:

Biker getBikerByNumber(int num);

you can't use it as an argument to funcName:

someObj.funcName(getBikerByNumber(42), myBikeArray, 42, ...); // won't compile

because rvalues to not bind to non-const references. They do bind to const references, though (and also to the rvalue references to be introduced by the next C++ standard and already implemented by some compilers).