Code question for the experts

Development Team
1

I’m trying to use float smoothed_airspeed defined in plane.h within the tiltrotor.cpp function Quadplane::tiltrotor_slew

There is a #include “plane.h” at the top of the file but compiling it comes back with 'smoothed_airspeed" was not declared in this scope.

What am I missing here? It’s probably dumb but it’s preventing me from perfecting my transition

TIA

2

Hi Andrew,

Definitely not an expert, but all you’ll have to do is use plane.smoothed_airspeed instead of just smoothed_airspeed in this case :slight_smile:

3

Actually, I learnt a few new things when I was going deeper into this, since I’m not very familiar with C++. I was wondering why the Quadplane class had access to the plane object in the first place.

It declares Plane as a friend class, so it has access to everything inside it:

public:
    friend class Plane`

But the real reason it sees a plane object at all is because in Plane.h, this is declared

extern Plane plane;

And this is (I think) filled up in Plane.cpp after the constructor. So the reason you needed to go through plane to get smoothed_airspeed is because smoothed_airspeed belongs to the Plane class, and what I’ve said here is why you can access plane in the first place.

This is probably pretty trivial, but just an interesting learning point for me :slight_smile:

4

Thanks @frizensami !

I don’t fully understand how it all hangs together yet but your solution fixed things up!

Remember too, in the valley of the blind, the one-eyed man is king! :smiley:

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