Angus Leeming wrote:
Richard Heck <[EMAIL PROTECTED]> writes:
This is very boring:
CommandInfo const * InsetCommandParams::findInfo(
InsetCode code, std::string const & cmdName)
{
switch (code) {
case BIBITEM_CODE:
return InsetBibitem::findInfo(cmdName);
case BIBTEX_CODE:
return InsetBibtex::findInfo(cmdName);
case CITE_CODE:
return InsetCitation::findInfo(cmdName);
case FLOAT_LIST_CODE:
return InsetFloatList::findInfo(cmdName);
case HFILL_CODE:
return InsetHFill::findInfo(cmdName);
What you're really implementing here is the Factory Pattern. One way to
implement a factory, as you're doing here, is using a giant switch. Another
way to do it is to register the content of the case statement in some map.
Something like (I probably get the function pointer syntax wrong):
class InsetCommandParams {
typedef CommandInfo const * (FindInfoFn *)(std::string);
static std::map<InsetCode, FindInfoFn *) findInfoFactory;
public:
static void RegisterFindInfo(InsetCode code, FindInfoFn * func)
{
findInfoFactory[code] = func;
}
};
class InsetBibitem {
static bool firstTime = true;
public:
InsetBibitem()
{
if (firstTime)
{
firstTime = false;
InsetCommandParams.RegisterFindInfo(BIBITEM_CODE,
InsetBibitem::findInfo);
}
}
};
Then your InsetCommandParams::findInfo just calls into the map:
CommandInfo const * InsetCommandParams::findInfo(
InsetCode code, std::string const & cmdName)
{
return findInfoFactory[code](cmdName);
}
Thanks very much. This really helps me understand this "registration"
thing. Possibly I'll try to implement this at some point, or just put a
FIXME suggesting someone else do it....
This is one place where c#'s reflection tool is a real win.
Don't know C#, but it's at points like this that I miss Perl:
sub findInfo {
$insetCode = shift;
$InsetType = getInsetName($insetCode);
no strict refs;
return $InsetType::findInfo();
}
Couldn't possibly be simpler. And in languages like Ruby, and I think
also Python, you can do even better, since types are objects.
rh
--
==================================================================
Richard G Heck, Jr
Professor of Philosophy
Brown University
http://frege.brown.edu/heck/
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