Help in OOP

[vsrajput@gmail.com]

Hi guys

I am not good OOP programmer ,trying to implement my already working
code in OOP.

I have somthing like this class.

class Datalogger{
public:
UINT Port;
BOOL bReady ;

Datalogger (UINT x ,bool y);
~Datalogger ();

bool LOpen ();
bool LStatus ();

};


Everything is OK till "bool LStatus ();"

bool LStatus ()
{
...... Here I have bunch of stuff;
but I get problem here

Waitforevent( Port , INFINTE , &bReady)
if(bReady)
{
.......
.....some stuff ;
.......

}
}


Where "Waitforeve nt" is fucntion came with driver of my I/O board .I
did not make this function.
it gives
bReady= true on events.

My question is that "CAN I USE member variable like this"
I means Can I use address of member variable to some function.

[Phlip]

Re: Help in OOP

vsrajput wrote:
[color=blue]
> I am not good OOP programmer ,trying to implement my already working
> code in OOP.[/color]

If that's just a learning thing that's cool. Don't do that on the job
because you shouldn't spend too much time changing code that already works.
[color=blue]
> I have somthing like this class.
>
> class Datalogger{
> public:
> UINT Port;
> BOOL bReady ;[/color]

Does anything assign bReady?

What did the following code look like before you OOP-ed it?
[color=blue]
> Waitforevent( Port , INFINTE , &bReady)
> if(bReady)[/color]
[color=blue]
> Where "Waitforeve nt" is fucntion came with driver of my I/O board .I
> did not make this function.
> it gives
> bReady= true on events.[/color]

Try adding this to the constructor:

Datalogger::Dat alogger(UINT x ,bool y): bReady(false) {}
[color=blue]
> My question is that "CAN I USE member variable like this"
> I means Can I use address of member variable to some function.[/color]

Yes, because the variable lives longer than the call to Waitforevent().
However, your variable might now contain garbage, and Waitforevent() might
read bReady's value and expect true or false.

--
Phlip
http://c2.com/cgi/wiki?ZeekLand <-- NOT a blog!!!

[Victor Bazarov]

Re: Help in OOP

vsrajput@gmail. com wrote:[color=blue]
> I have somthing like this class.
>
> class Datalogger{
> public:
> UINT Port;
> BOOL bReady ;
>
> Datalogger (UINT x ,bool y);
> ~Datalogger ();
>
> bool LOpen ();
> bool LStatus ();
>
> };
>
>
> Everything is OK till "bool LStatus ();"
>
> bool LStatus ()
> {
> ..... Here I have bunch of stuff;
> but I get problem here
>
> Waitforevent( Port , INFINTE , &bReady)
> if(bReady)
> {
> ......
> ....some stuff ;
> ......
>
> }
> }
>
>
> Where "Waitforeve nt" is fucntion came with driver of my I/O board .I
> did not make this function.
> it gives
> bReady= true on events.
>
> My question is that "CAN I USE member variable like this"
> I means Can I use address of member variable to some function.[/color]

Sure. What's the problem you're encountering?

V
--
Please remove capital 'A's when replying by e-mail
I do not respond to top-posted replies, please don't ask

[rageratwork@gmail.com]

Re: Help in OOP

vsrajput@gmail. com wrote:[color=blue]
> Hi guys
>
> I am not good OOP programmer ,trying to implement my already working
> code in OOP.
>
> I have somthing like this class.
>
> class Datalogger{
> public:
> UINT Port;
> BOOL bReady ;
>
> Datalogger (UINT x ,bool y);
> ~Datalogger ();
>
> bool LOpen ();
> bool LStatus ();
>
> };
>
>
> Everything is OK till "bool LStatus ();"
>
> bool LStatus ()
> {
> ..... Here I have bunch of stuff;
> but I get problem here
>
> Waitforevent( Port , INFINTE , &bReady)
> if(bReady)
> {
> ......
> ....some stuff ;
> ......
>
> }
> }
>
>
> Where "Waitforeve nt" is fucntion came with driver of my I/O board .I
> did not make this function.
> it gives
> bReady= true on events.
>
> My question is that "CAN I USE member variable like this"
> I means Can I use address of member variable to some function.[/color]

Yes you can...

....but in this case why? From what you have written, it looks like it
might be better if bReady was a local variable of LStatus(). Unless you
need to use the value in bReady somewhere else...

Dave

[vsrajput@gmail.com]

Re: Help in OOP

Hi guys ,

Thanks for your reply

Actually I want to use bReady in both member functions LStatus and
LOpen.

Thats why I didnt define bReady as local variable in LStatus.

But I solved my problem from ur suggestion.
What I did is follow.

bool LStatus ()
{
bool bbReady ; // defined one local variable
bbReady = bReady

Waitforevent( Port , INFINTE , &bbReady)
if(bbReady)
{
.......
.....some stuff ;
.......

}
}


Now everything is fine.
But I didnt understand why is this happing ,why cant I directly use
class member variable inside LStatus.
and If I make another copy of that variable inside LStatus ,then its
fine ??
Can anyone explain to me ??

[Victor Bazarov]

Re: Help in OOP

vsrajput@gmail. com wrote:[color=blue]
> Actually I want to use bReady in both member functions LStatus and
> LOpen.
>
> Thats why I didnt define bReady as local variable in LStatus.
>
> But I solved my problem from ur suggestion.
> What I did is follow.
>
> bool LStatus ()
> {
> bool bbReady ; // defined one local variable
> bbReady = bReady[/color]

There is no need in a separate assignment. Initialise!

bool bbReady = bReady;
[color=blue]
>
> Waitforevent( Port , INFINTE , &bbReady)
> if(bbReady)
> {
> ......
> ....some stuff ;
> ......
>
> }
> }
>
>
> Now everything is fine.
> But I didnt understand why is this happing ,why cant I directly use
> class member variable inside LStatus.[/color]

You can. Who said you couldn't?
[color=blue]
> and If I make another copy of that variable inside LStatus ,then its
> fine ??[/color]

What's the difference now? Did you have any problem before?
[color=blue]
> Can anyone explain to me ??[/color]

Explain what?

V
--
Please remove capital 'A's when replying by e-mail
I do not respond to top-posted replies, please don't ask

[vsrajput@gmail.com]

Re: Help in OOP

Yeah I understand i didnt need to do it in two statement. I can
initialise with declaration.

now my question is that i have a class .
class Datalogger{
public:
UINT Port;
BOOL bReady ;
Datalogger (UINT x ,bool y);
~Datalogger ();
bool LOpen ();
bool LStatus ();
};

Datalogger::Dat alogger(UINT x ,bool y){
Port = x;
bReady=y;}

Datalogger::LOp en(){

.....
.....
// it is also using bReady and Port and doing other stuff
....
}

Datalogger::LSt atus()
{
//it is also using bReady and Port in following manner.
Waitforevent( Port , INFINTE , &bReady) // waitforevent is a function
come with I/O driver
// It waits
for event and on event it makes bReady=true;
if(bReady)
{
.......
.....some stuff ;
.......
}
}

But if I am using bReady in this manner ,it gives in run time error and
program crashes.

[vsrajput@gmail.com]

Re: Help in OOP

Yeah I understand i didnt need to do it in two statement. I can
initialise with declaration.

now my question is that i have a class .
class Datalogger{
public:
UINT Port;
BOOL bReady ;
Datalogger (UINT x ,bool y);
~Datalogger ();
bool LOpen ();
bool LStatus ();
};

Datalogger::Dat alogger(UINT x ,bool y){
Port = x;
bReady=y;}

Datalogger::LOp en(){

.....
.....
// it is also using bReady and Port and doing other stuff
....
}

Datalogger::LSt atus()
{
//it is also using bReady and Port in following manner.
Waitforevent( Port , INFINTE , &bReady) // waitforevent is a function
come with I/O driver
// It waits
for event and on event it makes bReady=true;
if(bReady)
{
.......
.....some stuff ;
.......
}
}

But if I am using bReady in this manner ,it gives in run time error and
program crashes.

[rageratwork@gmail.com]

Re: Help in OOP


vsrajput@gmail. com wrote:[color=blue]
> Hi guys ,
>
> Thanks for your reply
>
> Actually I want to use bReady in both member functions LStatus and
> LOpen.
>[/color]

Ok, that's fine. Then you don't need the local variable.
[color=blue]
> But I didnt understand why is this happing ,why cant I directly use
> class member variable inside LStatus.[/color]

You can. There is no problem there.

Dave.

[Phlip]

Re: Help in OOP

vsrajput wrote:
[color=blue]
> Thanks for your reply[/color]

Does bReady contain garbage or did you make sure it's assigned correctly?
[color=blue]
> Actually I want to use bReady in both member functions LStatus and
> LOpen.[/color]

Does it convey a value between those two functions?

Never re-use a variable for a separate purpose, and never "prematurel y
optimize". Making the variable a member won't make it faster or anything.
Just make it local.
[color=blue]
> bool LStatus ()
> {
> bool bbReady ; // defined one local variable
> bbReady = bReady[/color]

You are missing a ;. This suggests you are not copying and pasting code into
your editor. Copying will be more accurate.
[color=blue]
> Waitforevent( Port , INFINTE , &bbReady)[/color]
[color=blue]
> Now everything is fine.
> But I didnt understand why is this happing ,why cant I directly use
> class member variable inside LStatus.[/color]

You can. Something else is going on. Does Waitforevent() store the address
of its argument so something can use it later, after the Waitforevent()
returns?
[color=blue]
> and If I make another copy of that variable inside LStatus ,then its
> fine ??
> Can anyone explain to me ??[/color]

Not with the current information. You probably still have undefined
behavior. That means anything could happen, including the program appears to
work correctly.

Specifically, using the & could lead to memory corruption. However, some
corruption doesn't crash a program immediately.

Write a unit test that stresses your class, and Waitforevent(), and if you
are still corrupting memory, calling the unit test many times may reveal the
corruption. However, it may reveal as a crash far from the source of your
bug.

--
Phlip
http://c2.com/cgi/wiki?ZeekLand <-- NOT a blog!!!

[Victor Bazarov]

Re: Help in OOP

vsrajput@gmail. com wrote:[color=blue]
> Yeah I understand i didnt need to do it in two statement. I can
> initialise with declaration.[/color]

Please use quoting when replying. It is useful [for others] to
see what you're replying to.
[color=blue]
> now my question is that i have a class .
> class Datalogger{
> public:
> UINT Port;
> BOOL bReady ;[/color]

Why are those data members public, BTW?
[color=blue]
> Datalogger (UINT x ,bool y);
> ~Datalogger ();
> bool LOpen ();
> bool LStatus ();
> };
>
> Datalogger::Dat alogger(UINT x ,bool y){
> Port = x;
> bReady=y;}[/color]

Prefer initialisation over assignment. See FAQ about that.
[color=blue]
>
> Datalogger::LOp en(){[/color]

bool Datalogger::LOp en(){
[color=blue]
>
> ....
> ....
> // it is also using bReady and Port and doing other stuff
> ...
> }
>
> Datalogger::LSt atus()[/color]

bool Datalogger::LSt atus()
[color=blue]
> {
> //it is also using bReady and Port in following manner.
> Waitforevent( Port , INFINTE , &bReady) // waitforevent is a function
> come with I/O driver
> // It waits
> for event and on event it makes bReady=true;[/color]

OK.
[color=blue]
> if(bReady)
> {
> ......
> ....some stuff ;
> ......
> }
> }
>
> But if I am using bReady in this manner ,it gives in run time error
> and program crashes.[/color]

Are you sure you're calling it for a valid object? What's the "this"
value in that function? How do you call this function?

V
--
Please remove capital 'A's when replying by e-mail
I do not respond to top-posted replies, please don't ask

[Phlip]

Re: Help in OOP

vsrajput wrote:
[color=blue]
> Yeah I understand i didnt need to do it in two statement. I can
> initialise with declaration.[/color]

Please include the replied-to text. Google makes this possible with
Reply->Preview->Edit. (Without that sequence, Google optimizes your post for
their viewer program, which not everyone uses.)
[color=blue]
> Datalogger::Dat alogger(UINT x ,bool y){
> Port = x;
> bReady=y;}[/color]

Okay. Post the code that calls Datalogger.

--
Phlip
http://c2.com/cgi/wiki?ZeekLand <-- NOT a blog!!!

[Joe Van Dyk]

Re: Help in OOP

vsrajput@gmail. com wrote:[color=blue]
> Yeah I understand i didnt need to do it in two statement. I can
> initialise with declaration.
>
> now my question is that i have a class .
> class Datalogger{
> public:
> UINT Port;
> BOOL bReady ;
> Datalogger (UINT x ,bool y);
> ~Datalogger ();
> bool LOpen ();
> bool LStatus ();
> };
>
> Datalogger::Dat alogger(UINT x ,bool y){
> Port = x;
> bReady=y;}[/color]

Horrible names, these are. Change 'x' and 'y' to something more meaningful.

[Joe Van Dyk]

Re: Help in OOP

vsrajput@gmail. com wrote:[color=blue]
> Hi guys
>
> I am not good OOP programmer ,trying to implement my already working
> code in OOP.
>
> I have somthing like this class.
>
> class Datalogger{
> public:
> UINT Port;[/color]

unsigned int Port;
[color=blue]
> BOOL bReady ;[/color]

bool bReady;
[color=blue]
>
> Datalogger (UINT x ,bool y);[/color]

Datalogger (unsigned int x, bool y);
[color=blue]
> ~Datalogger ();
>
> bool LOpen ();
> bool LStatus ();
>
> };
>
>
> Everything is OK till "bool LStatus ();"
>
> bool LStatus ()
> {
> ..... Here I have bunch of stuff;
> but I get problem here
>
> Waitforevent( Port , INFINTE , &bReady)
> if(bReady)
> {
> ......
> ....some stuff ;
> ......
>
> }
> }
>
>
> Where "Waitforeve nt" is fucntion came with driver of my I/O board .I
> did not make this function.
> it gives
> bReady= true on events.
>
> My question is that "CAN I USE member variable like this"
> I means Can I use address of member variable to some function.[/color]

Do you initialize bReady in the constructor initialization list?