type similar to union
Author
i need some kind of type that is like "union" that can store classes and when called returns the actual type that is currently set...
for example
class Base
{
union xtype
{
class1 A;
class1 B;
class1 C;
}
xtype U;
void class_function(class1 a){}
void class_function(class2 b){}
void class_function(class3 c){}
}
main()
{
Base X;
X.U = class1(somevalue);
Base.class_function(X.U); // call the apropriate function
}
how can i do this? ive looked at boost::variant but i dont think it allows me to call function inside the same class as the variable... since i have to make a "visitor" class which cant access variables in the class (which i need to).
I don't know the answer to your question, but maybe you could settle for something like the State pattern or the Strategy pattern?
Would using inheritance work for you instead?
main()
{
A a1;
Base *base = &a1
base->class_function();
}
[Edited by - Nypyren on January 8, 2008 3:45:05 PM]
__declspec(novtable) class Base{ virtual void class_function() = 0;};class A : public virtual Base //, other base classes{ virtual void class_function() {}};class B : public virtual Base //, etc{ virtual void class_function() {}};main()
{
A a1;
Base *base = &a1
base->class_function();
}
[Edited by - Nypyren on January 8, 2008 3:45:05 PM]
Author
Quote:Original post by Nypyren
Would using inheritance work for you instead?
im sorry i forgot to mention the regular types should also be used... i could make wrappers for all the types that i need though... but it seems like a quite ugly solution.. or?
EDIT:: Im using C++
Author
heh... well i guess soo... seems like i have a habit of simplifying my questions as much as possible...
i have a class which should store alot of objects/variables with different types and have "Set" functions for each type...
one way i could do this is to create on std::list<> for each type... but its a bit unpractical and ugly way to do it... also a bit slow where i have to decide which list to put new variables in...
what id like is a general type soo i can put all of them in the same list...
one way ive tried is to use boost::any... which works great except when i have to use "Set"... i have to first check which type it is than convert it to that type and call the appropriate "Set" function... which is kinda slow...
i have a class which should store alot of objects/variables with different types and have "Set" functions for each type...
one way i could do this is to create on std::list<> for each type... but its a bit unpractical and ugly way to do it... also a bit slow where i have to decide which list to put new variables in...
what id like is a general type soo i can put all of them in the same list...
one way ive tried is to use boost::any... which works great except when i have to use "Set"... i have to first check which type it is than convert it to that type and call the appropriate "Set" function... which is kinda slow...
Author
Quote:Original post by King Mir
Is the type X.U compile time constant?
im unsure what you mean...
Quote:Original post by Dragon_StrikeQuote:Original post by Nypyren
Would using inheritance work for you instead?
im sorry i forgot to mention the regular types should also be used... i could make wrappers for all the types that i need though... but it seems like a quite ugly solution.. or?
EDIT:: Im using C++
You'll have to make a separate class_function for every single type anyway, so making wrappers isn't THAT ugly.
Quote:Original post by Antheus
Why?
It's pointless to talk about solution without knowing the problem it's trying to solve.
Actually, talking about it helps a person understand available options so that they can make better decisions for totally different problems in the future.
Quote:Original post by Dragon_Strike
What I'd like is a general type so I can put all of them in the same list...
This is precisely the case where you'd want to use inheritance.
This topic is closed to new replies.
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