I may be asking this in a odd way, but I'm not sure how else to ask.
I want to have a list of classes, not objects. This way I can call static functions without have to create the object.
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Can you elaborate a bit more? What are you planning on doing with these classes? What static functions are you trying to call? Is this at compile-time or at runtime?templatetypedef– templatetypedef2011-01-29 05:47:06 +00:00Commented Jan 29, 2011 at 5:47
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I want to register a list of classes to a list in a factory class. Iterate over those classes to look for the one I need (using static methods) then instantiate it and return it.Jeremiah– Jeremiah2011-01-29 13:29:33 +00:00Commented Jan 29, 2011 at 13:29
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5 Answers
I would really prefer function pointers at this point:
struct A
{
void SomeFunc(int);
};
struct B
{
void AnotherFunc(int);
};
typedef void (*Function)(int);
std::vector<Function> vec;
vec.push_back(A::SomeFunc); vec.push_back(B::AnotherFunc);
for (Function f: vec)
{
f(2);
}
Note that a static function is more or less equivalent to a traditional C-function (it just got to access some more scope).
1 Comment
Jeremiah
I chose this route so I didn't have to use boost and I could practice implementing function pointers. Thanks
What you are looking for are boost typelists. I would however not recommend diving into the Boost MPL if you are not already very experienced with templates, and know how many of their intricacies work.
Now for a simple home-made implementation:
struct Null {};
template <typename Type, typename Next>
struct List
{
typedef Type Type;
typedef Next Next;
};
//Now you can make lists like so:
typedef List<int, List<float List<short, Null> > > MyList;
From there use recursive Templated implementations to call the static methods you want.
If you want more information on these kinds of techniques, you should read Modern C++ Design
2 Comments
Alexander Rafferty
There really should be more elegant solutions to these problems.
Fred Nurk
@AlexanderRafferty: 0x has variadic templates.
As a solution you can create a list of method pointers
Comments
I don't think what you are asking is possible, at least not in the way you think. You cannot have a variable, array, container class or any other storage of type names. So you cannot do something like
ListOfClasses[n]::someStaticMember(...);
in C++. It is impossible.
Comments
http://www.boost.org/doc/libs/1_45_0/libs/mpl/doc/refmanual/refmanual_toc.html
eg:
typedef vector<C1,C2,C3> types;
at_c<types,0>::type::method();
...
2 Comments
Alexander Rafferty
Your link isn't very helpful. Atleast explain what the're supposed to do with it.
Lara Bailey
Also, I really wouldn't recommend
using mpl::vector; or using namespace mpl;. The potential for confusion with std::vector is just too great.