Angus Leeming <[EMAIL PROTECTED]> writes:
| Attached is a simple sample showing how I could use boost::any to implement
| the transformation stuff in InsetExternal.
I do not agree with how you use operatesOn.
| template<typename Factory, typename Data>
| TransformCommand::ptr_type
| getTransformer(Data const & data) const {
| TransformCommand::ptr_type ptr;
|
| if (operatesOn(data)) {
| Factory factory = boost::any_cast<Factory>(value);
| ptr = factory(data);
| }
|
| return ptr;
| }
IMHO you should do the try/catch right there in getTransformer, no
need to do the any_cast twice.
template<typename Factory, typename Data>
TransformCommand::ptr_type
getTransformer(Data const & data) const {
TransformCommand::ptr_type ptr;
try {
Factory factor = boost::any_cast<Factory>(value);
ptr = factory(data);
}
catch (boost::bad_any_cast const &) {
}
return ptr;
}
Of course this functions really should just throw if wrong factory is
used, and not return a empty ptr in that case:
template<typename Factory, typename Data>
TransformCommand::ptr_type
getTransformer(Data const & data) const {
TransformCommand::ptr_type ptr;
Factory factor = boost::any_cast<Factory>(value);
return factory(data);
}
And the caller should handle the try and catch.
(getTransformer could catch the exception, but should rethrow it (as
another type perhaps).
| I think it results in very elegant code, but the killer is the try,catch
| block. The block is needed, so I guess that this means I cannot use the
| appropach within lyx?
If we all agree that we want to use exceptions, I am all for it.
But that is up to the rest of you.
| // This loop is all that needs go in insetexternal.C
| int main()
| {
| std::vector<TransformStore> factories;
| build(factories);
>
| RotationData rotationdata(30);
| ResizeData resizedata(2);
>
| string command = "\\input{foo}";
>
| std::vector<TransformStore>::const_iterator it = factories.begin();
| std::vector<TransformStore>::const_iterator end = factories.end();
| for (; it != end; ++it) {
| TransformCommand::ptr_type ptr;
| ptr = it->getTransformer<RotationFactory>(rotationdata);
| if (!ptr.get())
| ptr = it->getTransformer<ResizeFactory>(resizedata);
|
| if (ptr.get() == 0)
| continue;
>
| std::ostringstream os;
| os << ptr->front() << command << ptr->back();
| command = os.str();
| }
>
| std::cout << command << std::endl;
| }
for (; it != end; ++it) {
TransformCommand::ptr_type ptr;
try {
ptr =
it->getTransformer<RotationFactory>(rotationdata);
}
catch (...) {
try {
ptr =
it->getTransformer<ResizeFactory>(resizedata);
}
catch (...) {
continue;
}
}
std::ostringstream os;
os << ptr->front() << command << ptr->back();
command = os.str();
}
But I would rewrite a bit further to make it even simpler...
--
Lgb
