MARCO

[Wei-Chao Hsu]

Hi,


I read a Marco definition in a source file, which is shown below.


#define BEGIN_EVENT_TABLE(theClass, baseClass) \
const wxEventTable theClass::sm_eventTable = \
{ &baseClass::sm_eventTable, &theClass::sm_eventTableEntries[0] };

Because I am not a C++ expert, I don't understand the meaning of the
definition. Why does two variables, baseClass::sm_eventTable and
theClass::sm_eventTableEntries[0], appear in the braces at the same time.
Which value is assigned to theClass::sm_eventTable. Is there anyone could
explain for me? Thank you!



Dennis

 

[Rob Williscroft]

Wei-Chao Hsu wrote in

I read a Marco definition in a source file, which is shown below.
s/Marco/Macro/g



#define BEGIN_EVENT_TABLE(theClass, baseClass) \
const wxEventTable theClass::sm_eventTable = \
{ &baseClass::sm_eventTable,
&theClass::sm_eventTableEntries[0] };

Because I am not a C++ expert, I don't understand the meaning of the
definition. Why does two variables, baseClass::sm_eventTable and
theClass::sm_eventTableEntries[0], appear in the braces at the same
time. Which value is assigned to theClass::sm_eventTable. Is there
anyone could explain for me? Thank you!

theClass::sm_eventTable is an agragate and bothe values in the braces
get assigned to it.

A simple example:

#include <iostream>

struct XY
{
int x;
int y;
};

XY xy = { 1, 2 };

int main()
{
std::cerr << xy.x << '\n';
std::cerr << xy.y << '\n';
}

The output is:
1
2

HTH.

Rob.

 

[Jeffrey Schwab]

#define BEGIN_EVENT_TABLE(theClass, baseClass) \
const wxEventTable theClass::sm_eventTable = \
{ &baseClass::sm_eventTable, &theClass::sm_eventTableEntries[0] };

Because I am not a C++ expert, I don't understand the meaning of the
definition. Why does two variables, baseClass::sm_eventTable and
theClass::sm_eventTableEntries[0], appear in the braces at the same
time. Which value is assigned to theClass::sm_eventTable. Is there
anyone could explain for me? Thank you!

POLO!

If Rob's excellent example didn't clear help, try this:

http://www.devx.com/getHelpOn/Article/16039/0/page/3


-Jeff

 

[Wei-Chao Hsu]

Thanks for your help. I have understood.

#define BEGIN_EVENT_TABLE(theClass, baseClass) \
const wxEventTable theClass::sm_eventTable = \
{ &baseClass::sm_eventTable, &theClass::sm_eventTableEntries[0] };

Because I am not a C++ expert, I don't understand the meaning of the
definition. Why does two variables, baseClass::sm_eventTable and
theClass::sm_eventTableEntries[0], appear in the braces at the same
time. Which value is assigned to theClass::sm_eventTable. Is there
anyone could explain for me? Thank you!

POLO!

If Rob's excellent example didn't clear help, try this:

http://www.devx.com/getHelpOn/Article/16039/0/page/3


-Jeff