C / C++ / MFC

4-May-04 0:07

Case 1 is correct, because it returns a reference instead of a copy of this object.
See also:
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vccelng/htm/overl_14.asp[^]

Re: A question about OOP

toxcct4-May-04 0:09

toxcct

4-May-04 0:09

when you return a reference, you will be able tou chain the operators like this:

animal MyAnimal1, MyAnimal2, MyAnimal3;                    <font style="color:green;">// Declarations</font>
MyAnimal1 = animal(<font style="color:green;">/*accepted constructor parameters*/</font>);   <font style="color:green;">// here, both of the operator=() could work</font>
MyAnimal3 = MyAnimal2 = MyAnimal1;                         <font style="color:green;">// here, it must be a reference returned</font>

in general, we prefer the synopsis T& operator= (const T&)...
make your choice Smile | :)

TOXCCT >>> GEII power

Antony M Kancidrowski3-May-04 23:13

Antony M Kancidrowski

3-May-04 23:13

It may be a typo but if the code reflects what you have in your project you have missed a D out of DeleteMedia in the .cpp file.

In my experience if the function has not been defined in the header the autocompletion does not function.

Otherwise delete the project .ncb file and reload the project. This normally fixes such glitches.

Ant.

Jens Doose3-May-04 23:17

3-May-04 23:17

Two problems:
1. Intellisense sometimes has a problem with templates.
In that case you just have to type Wink | ;-)

2. You used a wrong syntax for declaring a template.
Also the methods of a template must be defined within
the header.
See the following example:

<br />
<br />
#include <vector><br />
using namespace std;<br />
<br />
template < class T > class CPlaylist<br />
{<br />
public:<br />
  CPlaylist(T m_vPlaylist)<br />
  {<br />
  };<br />
  virtual ~CPlaylist()<br />
  {<br />
  };<br />
  void DeleteMedia(int iPosition);<br />
<br />
protected:<br />
  std::vector< T > m_vPlaylist;<br />
  ...<br />
};<br />
<br />
template < class T > void CPlaylist< T >::DeleteMedia(int iPosition)<br />
{<br />
  ...<br />
}<br />
<br />

Jens

Anonymous3-May-04 23:39

3-May-04 23:39

We said me that when I work with the templates I have to define the function in the header file when they are declared... Is it true ?

When I define:

std::vector <t> m_vPlaylist;

Is this call correct?

m_vPlaylist.Erase(iPosition);

When I write "m_vPlaylist." I can't see all the functions that work with vectors... For example "Erase" function.

Jens Doose4-May-04 0:12

4-May-04 0:12

Well, try it Wink | ;-)

Your linker will complain about missing functions...

You cannot define
std::vector m_vPlaylist;
since std::vector is a template and therefor
it needs a type, a specialization like
std::vector< int > m_vPlaylist;
which will generate a vector for storing ints.

But anyway you cannot call erase with an int parameter,
it takes an iterator.

Jens

Antony M Kancidrowski4-May-04 2:53

Antony M Kancidrowski

4-May-04 2:53

Also note erase is all lower case.

Ant.

Anonymous4-May-04 3:41

4-May-04 3:41

How to define a constructor when using Templates?

Here is the one I've declared:
template<class t=""> CPlaylist<t>::CPlaylist(T m_csName)
{
}

with those protected variables:
vector <t> m_vPlaylist;
CString m_csName;

No problem at compilation but the functions I've declared after are unabled...

Function's declaration:

template<class t=""> void CPlaylist<t>::MyFunction()
{
//smthg
}

Jens Doose4-May-04 4:43

4-May-04 4:43

<br />
template < class T > class CPlaylist<br />
{<br />
public:<br />
  CPlaylist();<br />
  CPlaylist(T m_vPlaylist);<br />
  virtual ~CPlaylist();<br />
  void DeleteMedia(int iPosition);<br />
<br />
protected:<br />
  std::vector< T > m_vPlaylist;<br />
  CString m_csName; <br />
};<br />
<br />
template < class T > CPlaylist< T >::CPlaylist()<br />
{<br />
};<br />
<br />
template < class T > CPlaylist< T >::CPlaylist(T m_vPlaylist)<br />
{<br />
};<br />
<br />
template < class T > CPlaylist< T >::~CPlaylist()<br />
{<br />
};<br />
<br />
template < class T > void CPlaylist< T >::DeleteMedia(int iPosition)<br />
{<br />
  // Do smthg<br />
}<br />
<br />

Jens

Anonymous4-May-04 5:40

4-May-04 5:40

Thank's!
I have one last question... How to initialyse a variable which type is CPlaylist ?

CPlaylist <t> MyVariable;

??

Anonymous4-May-04 21:19

4-May-04 21:19

No idea on that... ?

Jens Doose5-May-04 5:45

5-May-04 5:45

Well, that really depends on your implementation of CPlayList...

Jens

Template

Anonymous3-May-04 23:03

3-May-04 23:03

Here is how I declare my template in my .h:

template<class t=""> class CPlaylist
{
public:
CPlaylist(T m_vPlaylist);
virtual ~CPlaylist();
void DeleteMedia(int iPosition);

protected:
vector <t> m_vPlaylist;
CString m_csName;
};

In my .cpp, I define my function:
template<class t=""> void CPlaylist<t>:eleteMedia(int iPosition)
{
m_vPlaylist.Erase(iPosition);
}

That compiles but I have no access to all of the Vector function when I write a "." . I can't see them...
Some ideas about that?

set time like a clock

Member 8209053-May-04 22:52

Member 820905

3-May-04 22:52

If i set one time in my application, I hope that it can act like a clock to notify me to do something at that time.
How can i achieve this?? Is there any Win32 API which can do this or some sample code that i can reference??

Thank in advance Big Grin | :-D

Joe Woodbury4-May-04 4:28

Joe Woodbury

4-May-04 4:28

Look up CreateWaitableTimer()/SetWaitableTimer()

(I last used this about three years ago at a different company so I have no source; sorry.)

Anyone who thinks he has a better idea of what's good for people than people do is a swine.
- P.J. O'Rourke

Member 8209054-May-04 15:55

Member 820905

4-May-04 15:55

If i create a thread to check if the time is up, is this the same with CreateWaitableTimer??

Thank you Wink | ;)

Joe Woodbury4-May-04 19:45

Joe Woodbury

4-May-04 19:45

Yes and no. You could do a timeout on a wait, but since the system clock can slip, the longer the timeout, the worse the precision. You're also limited to a relatively short period of time.

An alternative, which I have also used, is to have the thread wake up every hour, or some time period, check the time, then go back into the wait with a timeout (the wait was monitoring a shutdown event for graceful exit.)

Anyone who thinks he has a better idea of what's good for people than people do is a swine.
- P.J. O'Rourke

Member 8209054-May-04 20:05

Member 820905

4-May-04 20:05

If the thread wake up every hour, i set the clock between one hour scale.
Will i lose the chance to get the correct time??

I don't know why should go back into the wait with a timeout??

Thank for your help Big Grin | :-D

why not to open <graphics.h>in vc++?

Joe Woodbury5-May-04 6:31

Joe Woodbury

5-May-04 6:31

Givens:

1) hEvent is a handle to an event
2) the following is in a thread
3) proper initialization has been done

for (;;)<br />
{<br />
  // 60 * 60 * 1000 is one hour<br />
  if (WaitForSingleObject(hEvent, 60 * 60 * 1000) != WAIT_TIMEOUT)<br />
    break;<br />
<br />
  SYSTEMTIME time;<br />
  GetSystemTime(&time);<br />
  // check if time meets your criteria. If so, do something. If not,<br />
  // wait another hour (or specified period of time)<br />
  // Be aware that this DOES NOT compensate for daylight savings time<br />
  // nor does it factor in clock drift in a system. If you need to<br />
  // wait for a precise time, the only reliable method is the one I<br />
  // gave earlier<br />
}

Anyone who thinks he has a better idea of what's good for people than people do is a swine.
- P.J. O'Rourke

vividtang3-May-04 22:38

vividtang

3-May-04 22:38

what's the difference when opening the file between in the way of text and
in the way of binary system?

Re: why not to open <graphics.h>in vc++?

Jens Doose3-May-04 22:57