C / C++ / MFC

9-Oct-02 6:28

set

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Re: STL and intrinsic sorting

Joaquín M López Muñoz9-Oct-02 8:04

Joaquín M López Muñoz

9-Oct-02 8:04

set and map (the ordering in the latter is done by the key).

Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo

Re: STL and intrinsic sorting

ns9-Oct-02 8:45

9-Oct-02 8:45

Thanks for letting me know its sorted on the key.I was wondering.... Smile | :)

Appreciate your help,
ns

Pointers to virtual methods

Patje9-Oct-02 6:23

Patje

9-Oct-02 6:23

Hi gurus,

Suppose you have some classes like these:

class BaseClass<br />
   {<br />
   public: virtual long getValue() {return 0;}<br />
   };<br />
<br />
class SubClass1 : public BaseClass<br />
   {<br />
   public: virtual long getValue() {return 1;}<br />
   };<br />
<br />
class SubClass2 : public BaseClass<br />
   {<br />
   };<br />
<br />
void SomeFun (BaseClass *someInstance)<br />
{<br />
// Find out if getValue has been overruled or not<br />
// i.e. which function is called by someInstance->getValue<br />
}<br />
<br />
int main (int argc, char **argv)<br />
{<br />
BaseClass baseInstance;<br />
SubClass1 subInstance1;<br />
SubClass2 subInstance2;<br />
<br />
SomeFun (&baseInstance);<br />
SomeFun (&subInstance1);<br />
SomeFun (&subInstance2);<br />
}

In other words, in SomeFun I want to find out which implementation of getValue is used by the given instance. I don't want to actually call someInstance->getValue, but I just want to find out which method would be called if I would call it.

I tried to find the address of the method by using
&someInstance->getValue
and
someInstance->getValue
but the first one doesn't compile, and the second one gives a warning and doesn't work.

Notice I don't want to use something like
pMethod = BaseClass::getValue;
or
pMethod = SubClass1::getValue;
since I don't know who has inherited from my BaseClass, nor which instance is given as argument to me. I just want to know: the class of which an instance is given to me, has it overruled the virtual method getValue or not?

Of course a solution could be to add another virtual method, something like:
bool iHaveOverruledGetValue();
which should be implemented by each subclass (if they have overruled the getValue method, but that doesn't seem like a good solution either.

Anyone suggestions ?

Enjoy life, this is not a rehearsal !!!

Re: Pointers to virtual methods

C^hris L^osinger9-Oct-02 6:22

9-Oct-02 6:22

Patje wrote:
Of course a solution could be to add another virtual method

IMHO, that seems like the best approach, both from an OO standpoint and a maintainability one. otherwise, with the pointer idea, you're writing code that is at best confusing and at worst non-portable.

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Re: Pointers to virtual methods

Todd Smith9-Oct-02 19:10

Todd Smith

9-Oct-02 19:10

You can create a switch statement and try dynamic_cast but that requries RTTI to be enabled.

I would just add a virtual method.

Todd Smith

OnDropdown NOT!

jimNLX9-Oct-02 6:08

jimNLX

9-Oct-02 6:08

is there a way to stop this from open when a certain condition is met?

I'm trying to do this in the OnDropdown section of code and anything I do dosen't stop the dropdown from opening.

Thanks for your help,

Jim

Re: OnDropdown NOT!

Maximilien9-Oct-02 6:15

Maximilien

9-Oct-02 6:15

I assume it's for a combox box, why can't you just disable the control ?
the OnDropDown is the callback.
Max.

Re: OnDropdown NOT!

jimNLX9-Oct-02 6:26

jimNLX

9-Oct-02 6:26

Here is what the code looks like. I couldn't find anything that would just quite without displaying that drop down.

void CAMID::OnDropdownMSel()
{
CComboBox *pMSelBox = (CComboBox *) GetDlgItem(IDC_MISSION_SEL);

if(HostStruct.bFreeze == false)
{//warn user...and quit dropdown
MessageBox("blah blah blah", "Warning!", MB_OK);

}
else
{
//drop down box
}

putting in leading spaces

ns9-Oct-02 5:59

9-Oct-02 5:59

I have strings (numeric) of various lengths:

"123"
"2345"
"5"
"99999"
etc. I need to make them all as long as the longest one "99999", so they should look like "00123", "00005", etc.

If these strings are stored in an array A[], then how can I do this padding? I will be knowing the biggest strings length.
I need to automate this process.

for ( int i = 0; i

jmkhael9-Oct-02 6:05

jmkhael

9-Oct-02 6:05

use CStrings if u can

CString urString;

in the loop:

urString = a [i];
CString t( '0', numberOfSpaceNeeded ); 
t += urString;

Papa

while (TRUE)
Papa.WillLove ( Bebe ) ;

ns9-Oct-02 6:11

9-Oct-02 6:11

Amazing! Thanks! I didnt know CString had such a handy constructor..... Smile | :)

Appreciate your help,
ns

Maximilien9-Oct-02 6:25

Maximilien

9-Oct-02 6:25

You could format the number with the approprite lenghth

CString aString;
aString.Format( "%7i", 123 ); // where the string will have a lenght of 7 chars.

Joe Woodbury9-Oct-02 7:00

Joe Woodbury

9-Oct-02 7:00

Maximilien wrote:

CString aString;<br /> aString.Format( "%7i", 123 ); // where the string will have a lenght of 7 chars.

You forgot the zero:

aString.Format("%07i", 123);

member in thread procedure

Maximilien9-Oct-02 7:10

Maximilien

9-Oct-02 7:10

yep!

Thanks.

stevenson9-Oct-02 5:33

stevenson

9-Oct-02 5:33

I write a class which kicks off a thread in constructor and terminated it in destroyer. This thread has a message queue, and in the switch-case, calls the class' member functions or member variables. And so far, I got the following reward WTF | :WTF:

:

illegal call of non-static member function

In my point of view, It's reasonable to use massage queue to manage member functions and member variables. it sounds good but I kick a stone, tell me why and how to make a difference.

Thanks

Extreme programming. Do the No.1

Re: member in thread procedure

C^hris L^osinger9-Oct-02 5:44

9-Oct-02 5:44

a thread function (the one that you use to start the thread) cannot be a member function of a class, unless that function is static.

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Re: member in thread procedure

stevenson9-Oct-02 5:56

stevenson

9-Oct-02 5:56

why??? why must be static? u mean serval instances have only one thread function? then once again, how to call a member funtion in a thread function?

What's happening in backyard?

thanks

Extreme programming. Do the No.1

Re: member in thread procedure

C^hris L^osinger9-Oct-02 6:12

9-Oct-02 6:12

stevenson wrote:
why??? why must be static?

the thread proc can't be a non-static member function because there is no way to provide the "this" pointer to provide an object context for that member function to be called from. it's like this:

int i = CString::GetLength();

GetLength makes no sense without an actual CString object. a static member function doesn't require an actual object instance, so you can use it as a thread proc.

you can pass an object into the thread proc and use it indirectly:

volatile dataStruct data; 
data.pMyObject = &TheObjectIWantToUse;
AfxBeginThread(ThreadProc, (void *)&data, THREAD_PRIORITY_NORMAL, 0, CREATE_SUSPENDED);

...

UINT ThreadProc(void *p)
{
   dataStruct *pData = (dataStruct *)p;

   now you can use pData->pMyObject;
}

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