C++ Question Breaking a monster-sized class into multiple sub-classes - Orbiter-Forum

**Hlynkacg** · 08-19-2012, 08:32 PM

Like the title says, I need help breaking a monster-sized (vessel) class into more managable sub-classes.

Specifically I want to take my Lunar Lander's autopilot functions/variables and (for the sake of readability) place them in their own class.

However the base vessel class still needs acces to some of those variables for situations like.

Code:

if (ThrotControlAuto()) SetThrusterGroupLevel(THGROUP_HOVER, AP_CommandedThrust);

I tried copying the syntax of the DG's AAP but that hasn't worked

As per the DG example LEM_AP is defined as a friend class to SpiderLEM (my vessel class)

Code:

class SpiderLEM: public VESSEL3 {
	friend class LEM_AP;	// LEM Autopilot Class

public:
	SpiderLEM (OBJHANDLE hVessel, int flightmodel);
	~SpiderLEM ();
...

The LEM_AP class itself looks like this

Code:

// ==============================================================
//		ORBITER MODULE: 'SPIDER' LUNAR EXCURSION MODULE
//			A custom Vessel For Orbiter 2010/2011
//  
// LEM_Autopilots.h
// Class interface for Lunar Excursion Module Autopilot
// ==============================================================

#include "Orbitersdk.h"
#include "SpiderLEM.h"

class VESSEL3;

class LEM_AP: public SpiderLEM {
public:
	LEM_AP (VESSEL3 *v);
	virtual ~LEM_AP ();

	// Autopilot Functions
	void	OrientForBurn(VECTOR3& tgtVector);
	void	SetPitch(double tgtPitch);
	void	SetRoll(double tgtRoll);
	void	SetHdg(double tgtHdg);
	void	AutoHover(void);
	void	AutoAscent(double simt);
	void	AutoLand(double simt);

	double	rRate;
	double	AP_CommandedThrust, AP_CommandedYaw, AP_CommandedRoll, AP_CommandedPitch; // Autopilot control inputs

protected:
	VESSEL3 *vessel;
	
private:
	int		AP_ProgState; // current autopilot program state
};

Finally we have the .cpp file which looks like this...

Code:

#include "LEM_Autopilots.h"

LEM_AP::LEM_AP (SpiderLEM *vessel)
{
}

LEM_AP::~LEM_AP ()
{
}
Assorted Functions beyond this point...

As it stands I'm getting a compiler error wich states that the LEM_AP constructor is invalid.

If I comment the constructor out the code compiles but I am unable to call any of LEM_AP's functions.

Please help a C++ noob figure this out.

**orb** · 08-19-2012, 08:49 PM

Quote:

Originally Posted by Hlynkacg

Code:

class LEM_AP: public SpiderLEM {
public:
	LEM_AP (VESSEL3 *v);

Code:

LEM_AP::LEM_AP (SpiderLEM *vessel)
{
}

As it stands I'm getting a compiler error wich states that the LEM_AP constructor is invalid.

Did you try this way instead?:

Code:

LEM_AP::LEM_AP (VESSEL3 *vessel) : SpiderLEM (vessel) {
}

EDIT: It won't work though, because SpiderLEM's constructor is different:

Code:

SpiderLEM (OBJHANDLE hVessel, int flightmodel);

You need an OBJHANDLE of the vessel and flghtmodel to be passed to the SpiderLEM's constructor.

Are you sure you want to extend the SpiderLEM class with LEM_AP or only make it a friend class?

**Hlynkacg** · 08-19-2012, 09:25 PM

Quote:

Originally Posted by orb

Did you try this way instead?:

Code:

LEM_AP::LEM_AP (VESSEL3 *vessel) : SpiderLEM (vessel) {
}

EDIT: It won't work though, because SpiderLEM's constructor is different:

Code:

SpiderLEM (OBJHANDLE hVessel, int flightmodel);

I did and as you said, it didn't work.

Code:

You need an OBJHANDLE of the vessel and flghtmodel to be passed to the SpiderLEM's constructor.

How would I go about doing this?

Quote:

Are you sure you want to extend the SpiderLEM class with LEM_AP or only make it a friend class?

No, I'm not sure.

My problem is simply that the class definition for SpiderLEM itself is rapidly becoming unmanageably large. I thought that breaking various sub-systems off into thier own sub-classes would help counter this.

**orb** · 08-19-2012, 09:33 PM

When you extend SpiderLEM class, which extends VESSEL3 class, you basically create another vessel class based on SpiderLEM, so another vessel. If LEM_AP is just SpiderLEM's autopilot, it shouldn't extend SpiderLEM. Remove ": public SpiderLEM" from the class declaration.

**Hlynkacg** · 08-19-2012, 09:38 PM

Quote:

Originally Posted by orb

When you extend SpiderLEM class, which extends VESSEL3 class, you basically create another vessel class based on SpiderLEM, so another vessel. If LEM_AP is just SpiderLEM's autopilot, it shouldn't extend SpiderLEM. Remove ": public SpiderLEM" from the class declaration.

So the class declaration should look like...

Code:

class LEM_AP {
public:
	LEM_AP (VESSEL3 *v);
	virtual ~LEM_AP ();

	// Autopilot Functions

?

**orb** · 08-19-2012, 09:42 PM

Quote:

Originally Posted by Hlynkacg

So the class declaration should look like...

Yes. If you need to access protected members of SpiderLEM, you want to add "friend class SpiderLEM;" to its declaration, too.

**Hlynkacg** · 08-19-2012, 09:55 PM

Ok,

made the change and added SpiderLEM (the primary vessel class) as a friend of LEM_AP.

Now the compiler error I'm geting is lots of undeclared identifiers.

Functions with the "SpiderLEM::" prefix are marked "illegal reference to non-static member"

Do I tell it to get those values from SpiderLEM?

Am I going to have to redeclare them?

**orb** · 08-19-2012, 10:02 PM

Quote:

Originally Posted by Hlynkacg

Functions with the "SpiderLEM::" prefix are marked "illegal reference to non-static member"

You don't reference non-static members with:

Code:

SpiderLEM::member

but with the variable holding pointer to instance of the SpiderLEM class:

Code:

vessel->member

**Hlynkacg** · 08-19-2012, 10:46 PM

What if the variable or function in question is unique to SpiderLEM (not a member of the VESSEL3 class)?

Likewise How do I call LEM_AP functions from within Spider?

marooder86 · 08-19-2012, 10:59 PM

Quote:

Originally Posted by Hlynkacg

Likewise How do I call LEM_AP functions from within Spider?

Depends on how you create the autopilot in lander class. If it something like

Code:

class Lander
{
...
LEM_AP autopilot;
};

then you call it's functions like that

Code:

//somewhere in code
...
autopilot.some_autopilot_function()
...

If you ceate your autopilot dynamically then you call it's functions with pointer that points to it.

Code:

class Lender
{
...
LEM_AP *autopilot;
};

//somewhere in code
...
autopilot->some_autopilot_function()
...

And by the way, if you don't use virtual functions in your autopilot class then it's destructor doesn't have to be virtual, the ordinary one will do just fine.
One more thing is if you haven't corrected it already. You've declared such constructor in your autopilot class

Code:

LEM_AP (VESSEL3 *v);

and you're trying to implement it this way

Code:

LEM_AP::LEM_AP (SpiderLEM *vessel)
{
}

and those are two completely diffrent constructors, you have to implement what you've declared

Code:

LEM_AP::LEM_AP (VESSEL3 *vessel)
{
}

**orb** · 08-19-2012, 11:02 PM

Quote:

Originally Posted by Hlynkacg

What if the variable or function in question is unique to SpiderLEM (not a member of the VESSEL3 class)?

Is `vessel` always holding an instance of SpiderLEM class? If so, you should have declared it as `SpiderLEM * vessel`. If it can hold instance of other vessel class based on VESSEL3, you can do `((SpiderLEM *)vessel)->member` after checking if the `vessel` is of `SpiderLEM` class.

**Hlynkacg** · 08-20-2012, 01:23 AM

Quote:

Originally Posted by marooder86

Depends on how you create the autopilot in lander class. If it something like

Code:

class Lander
{
...
LEM_AP autopilot;
};

then you call it's functions like that

Code:

//somewhere in code
...
autopilot.some_autopilot_function()
...

If you ceate your autopilot dynamically then you call it's functions with pointer that points to it.

Code:

class Lender
{
...
LEM_AP *autopilot;
};

//somewhere in code
...
autopilot->some_autopilot_function()
...

Are there advantages to doing it one way over the other?

Quote:

Originally Posted by orb

Is `vessel` always holding an instance of SpiderLEM class? If so, you should have declared it as `SpiderLEM * vessel`. If it can hold instance of other vessel class based on VESSEL3, you can do `((SpiderLEM *)vessel)->member` after checking if the `vessel` is of `SpiderLEM` class.

At the moment it will always be an instance of "SpiderLEM" but I do have plans to expand in that I eventually want to develope a whole family of "Spiders" that share a common functionality.

Uderstand that aside from having a pretty strong math background I'm coming into this armed with little more than the Orbiter API documentation, and a C++ for beginners turorial.

I've gotten as far as I have by copying/modifying the SDK samples and through help from this very forum.

---------- Post added at 01:23 AM ---------- Previous post was at 12:26 AM ----------

Another quick question...

if I add a clbkPreStep or clbkPostStep to my LEM_AP class will orbiter call it?

it'd be nice from a code readability stand point if I could move AP's "house keeping" along with the AP.

**orb** · 08-20-2012, 04:58 AM

Quote:

Originally Posted by Hlynkacg

At the moment it will always be an instance of "SpiderLEM" but I do have plans to expand in that I eventually want to develope a whole family of "Spiders" that share a common functionality.

As long as all of them will extend some common class, you can declare the `vessel` variable to point to that class, be it a `SoiderLEM` or a `Spider` class (but then SpiderLEM will need to extend the Spider class extending the VESSEL3 class, and not just VESSEL3 class).

Quote:

Originally Posted by Hlynkacg

if I add a clbkPreStep or clbkPostStep to my LEM_AP class will orbiter call it?

They won't be called. LEM_AP class isn't registered in Orbiter to receive such calls. It's your own class. You need to call autopilot functions which must be called in each step from the vessel's clbkPreStep or clbkPostStep.

marooder86 · 08-20-2012, 01:06 PM

Quote:

Originally Posted by Hlynkacg

Are there advantages to doing it one way over the other?

It's not the matter of adventage of one option over the other as it'a matter of program design you've choosed. There are situations when storing object of one class as a member of another one are desirable and logical solution, and there are times when pointer option is better or you simply have no other way of implementing it. For example when the object of a class(let's call it classB) which is a member of another class(classA) does not exist at the point of program execution where you're creating classA object then you have to use pointer solution and wait for classB object to be created so you can get the pointer to it.
From my point of view, in your case both ways would be equally good, although personally I would go with the first option(storing the actual object as a member) since both classes are strongly interconnected and depand on each other existance.
But you know, that's only my

.

**Hlynkacg** · 08-20-2012, 05:11 PM

I'm probably missing something obvious so bear with me...

I added to

"class LM_AP Autopilot;"

to my SpiderLEM class but the compiler is flagging it as undeclared.

do I have to include my LEM_Autopilot.h file in SpiderLEM.h? (or move the class declaration to SpiderLEM.h?)

If so wouldn't this cause issues with recursion? (LEM_Autopilot.h includes SpiderLEM.h)

08-19-2012, 08:49 PM	#2
orb O-F Administrator	Quote: Originally Posted by Hlynkacg Code: class LEM_AP: public SpiderLEM { public: LEM_AP (VESSEL3 v); Code: LEM_AP::LEM_AP (SpiderLEM vessel) { } As it stands I'm getting a compiler error wich states that the LEM_AP constructor is invalid. Did you try this way instead?: Code: LEM_AP::LEM_AP (VESSEL3 *vessel) : SpiderLEM (vessel) { } EDIT: It won't work though, because SpiderLEM's constructor is different: Code: SpiderLEM (OBJHANDLE hVessel, int flightmodel); You need an OBJHANDLE of the vessel and flghtmodel to be passed to the SpiderLEM's constructor. Are you sure you want to extend the SpiderLEM class with LEM_AP or only make it a friend class?

08-19-2012, 09:25 PM	#3
Hlynkacg Aspiring rocket scientist	Quote: Originally Posted by orb Did you try this way instead?: Code: LEM_AP::LEM_AP (VESSEL3 *vessel) : SpiderLEM (vessel) { } EDIT: It won't work though, because SpiderLEM's constructor is different: Code: SpiderLEM (OBJHANDLE hVessel, int flightmodel); I did and as you said, it didn't work. Code: You need an OBJHANDLE of the vessel and flghtmodel to be passed to the SpiderLEM's constructor. How would I go about doing this? Quote: Are you sure you want to extend the SpiderLEM class with LEM_AP or only make it a friend class? No, I'm not sure. My problem is simply that the class definition for SpiderLEM itself is rapidly becoming unmanageably large. I thought that breaking various sub-systems off into thier own sub-classes would help counter this.

08-19-2012, 09:38 PM	#5
Hlynkacg Aspiring rocket scientist	Quote: Originally Posted by orb When you extend SpiderLEM class, which extends VESSEL3 class, you basically create another vessel class based on SpiderLEM, so another vessel. If LEM_AP is just SpiderLEM's autopilot, it shouldn't extend SpiderLEM. Remove ": public SpiderLEM" from the class declaration. So the class declaration should look like... Code: class LEM_AP { public: LEM_AP (VESSEL3 *v); virtual ~LEM_AP (); // Autopilot Functions ?

08-19-2012, 10:02 PM	#8
orb O-F Administrator	Quote: Originally Posted by Hlynkacg Functions with the "SpiderLEM::" prefix are marked "illegal reference to non-static member" You don't reference non-static members with: Code: SpiderLEM::member but with the variable holding pointer to instance of the SpiderLEM class: Code: vessel->member

08-19-2012, 10:46 PM	#9
Hlynkacg Aspiring rocket scientist	What if the variable or function in question is unique to SpiderLEM (not a member of the VESSEL3 class)? Likewise How do I call LEM_AP functions from within Spider? Last edited by Hlynkacg; 08-19-2012 at 10:52 PM.

08-19-2012, 09:33 PM	#4
orb O-F Administrator	When you extend SpiderLEM class, which extends VESSEL3 class, you basically create another vessel class based on SpiderLEM, so another vessel. If LEM_AP is just SpiderLEM's autopilot, it shouldn't extend SpiderLEM. Remove ": public SpiderLEM" from the class declaration.

08-19-2012, 09:42 PM	#6
orb O-F Administrator	Quote: Originally Posted by Hlynkacg So the class declaration should look like... Yes. If you need to access protected members of SpiderLEM, you want to add "friend class SpiderLEM;" to its declaration, too.

08-19-2012, 09:55 PM	#7
Hlynkacg Aspiring rocket scientist	Ok, made the change and added SpiderLEM (the primary vessel class) as a friend of LEM_AP. Now the compiler error I'm geting is lots of undeclared identifiers. Functions with the "SpiderLEM::" prefix are marked "illegal reference to non-static member" Do I tell it to get those values from SpiderLEM? Am I going to have to redeclare them?

08-19-2012, 10:59 PM	#10
marooder86 Orbinaut	Quote: Originally Posted by Hlynkacg Likewise How do I call LEM_AP functions from within Spider? Depends on how you create the autopilot in lander class. If it something like Code: class Lander { ... LEM_AP autopilot; }; then you call it's functions like that Code: //somewhere in code ... autopilot.some_autopilot_function() ... If you ceate your autopilot dynamically then you call it's functions with pointer that points to it. Code: class Lender { ... LEM_AP autopilot; }; //somewhere in code ... autopilot->some_autopilot_function() ... And by the way, if you don't use virtual functions in your autopilot class then it's destructor doesn't have to be virtual, the ordinary one will do just fine. One more thing is if you haven't corrected it already. You've declared such constructor in your autopilot class Code: LEM_AP (VESSEL3 v); and you're trying to implement it this way Code: LEM_AP::LEM_AP (SpiderLEM vessel) { } and those are two completely diffrent constructors, you have to implement what you've declared Code: LEM_AP::LEM_AP (VESSEL3 vessel) { } Last edited by marooder86; 08-19-2012 at 11:09 PM.

08-19-2012, 11:02 PM	#11
orb O-F Administrator	Quote: Originally Posted by Hlynkacg What if the variable or function in question is unique to SpiderLEM (not a member of the VESSEL3 class)? Is `vessel` always holding an instance of SpiderLEM class? If so, you should have declared it as `SpiderLEM * vessel`. If it can hold instance of other vessel class based on VESSEL3, you can do `((SpiderLEM *)vessel)->member` after checking if the `vessel` is of `SpiderLEM` class.

08-20-2012, 01:23 AM	#12
Hlynkacg Aspiring rocket scientist	Quote: Originally Posted by marooder86 Depends on how you create the autopilot in lander class. If it something like Code: class Lander { ... LEM_AP autopilot; }; then you call it's functions like that Code: //somewhere in code ... autopilot.some_autopilot_function() ... If you ceate your autopilot dynamically then you call it's functions with pointer that points to it. Code: class Lender { ... LEM_AP autopilot; }; //somewhere in code ... autopilot->some_autopilot_function() ... Are there advantages to doing it one way over the other? Quote: Originally Posted by orb* Is `vessel` always holding an instance of SpiderLEM class? If so, you should have declared it as `SpiderLEM * vessel`. If it can hold instance of other vessel class based on VESSEL3, you can do `((SpiderLEM *)vessel)->member` after checking if the `vessel` is of `SpiderLEM` class. At the moment it will always be an instance of "SpiderLEM" but I do have plans to expand in that I eventually want to develope a whole family of "Spiders" that share a common functionality. Uderstand that aside from having a pretty strong math background I'm coming into this armed with little more than the Orbiter API documentation, and a C++ for beginners turorial. I've gotten as far as I have by copying/modifying the SDK samples and through help from this very forum. ---------- Post added at 01:23 AM ---------- Previous post was at 12:26 AM ---------- Another quick question... if I add a clbkPreStep or clbkPostStep to my LEM_AP class will orbiter call it? it'd be nice from a code readability stand point if I could move AP's "house keeping" along with the AP.

08-20-2012, 04:58 AM	#13
orb O-F Administrator	Quote: Originally Posted by Hlynkacg At the moment it will always be an instance of "SpiderLEM" but I do have plans to expand in that I eventually want to develope a whole family of "Spiders" that share a common functionality. As long as all of them will extend some common class, you can declare the `vessel` variable to point to that class, be it a `SoiderLEM` or a `Spider` class (but then SpiderLEM will need to extend the Spider class extending the VESSEL3 class, and not just VESSEL3 class). Quote: Originally Posted by Hlynkacg if I add a clbkPreStep or clbkPostStep to my LEM_AP class will orbiter call it? They won't be called. LEM_AP class isn't registered in Orbiter to receive such calls. It's your own class. You need to call autopilot functions which must be called in each step from the vessel's clbkPreStep or clbkPostStep.

08-20-2012, 01:06 PM	#14
marooder86 Orbinaut	Quote: Originally Posted by Hlynkacg Are there advantages to doing it one way over the other? It's not the matter of adventage of one option over the other as it'a matter of program design you've choosed. There are situations when storing object of one class as a member of another one are desirable and logical solution, and there are times when pointer option is better or you simply have no other way of implementing it. For example when the object of a class(let's call it classB) which is a member of another class(classA) does not exist at the point of program execution where you're creating classA object then you have to use pointer solution and wait for classB object to be created so you can get the pointer to it. From my point of view, in your case both ways would be equally good, although personally I would go with the first option(storing the actual object as a member) since both classes are strongly interconnected and depand on each other existance. But you know, that's only my .

08-20-2012, 05:11 PM	#15
Hlynkacg Aspiring rocket scientist	I'm probably missing something obvious so bear with me... I added to "class LM_AP Autopilot;" to my SpiderLEM class but the compiler is flagging it as undeclared. do I have to include my LEM_Autopilot.h file in SpiderLEM.h? (or move the class declaration to SpiderLEM.h?) If so wouldn't this cause issues with recursion? (LEM_Autopilot.h includes SpiderLEM.h)

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