Vector of a template class into another class

[caneta]

Hi everybody.
I have a template class which works fine:

template<class T>
class Flag {
	string flagName;
	vector<T> paramList;
	typename vector<T>::iterator it;

	public:
	Flag <T>(string, string, bool);
};

The problem is that I have another class which should store a vector of object of the first class, but I have no idea on how to implement it. It should be something like:

class CmdLine {

	Module *module;
	vector<Flag<T> > cmdLineVect; // WRONG!!!

	public:
	CmdLine (Module*);
	~CmdLine (void);
	
	void addFlag(Flag<T> );
};

But of course it does not work...
Could you give me some advices? What are the possible ways to achieve my goal?
Thanks in advance!

[guestgulkan]

class CmdLine is not a template class, so the T on these two line here:
vector<Flag<T> > cmdLineVect;
void addFlag(Flag<T> );
have no relevance.

Turn them concrete types - For example

vector<Flag<int> > cmdLineVect;
void addFlag(Flag<int> );

or turn CmdLine into a template class as well.

 template<typename T>
class CmdLine {

	Module *module;
	vector<Flag<T> > cmdLineVect; 

	public:
	CmdLine (Module*);
	~CmdLine (void);
	
	void addFlag(Flag<T> );
};

[caneta]

Turning them into a concrete type makes no sense to me, because I loose the power of template implementation.

Your second suggestion is not duable too, because if I do this

CmdLine <int> *commandLine = new CmdLine<int> (prog);

I create an object CmdLine with a vector of object Flag<int>. But this is not what I want.

I would like to define a vector that could store for example one Flag<int>, one Flag<float> and one Flag<string>.

Is that possible? I'm wondering if it's possible to do something like that with inheritance...

Or maybe my approach is simply wrong...

[kbw]

Or maybe my approach is simply wrong...

You seem to need a variant. That's been discussed recently.
jsmith's example may help. http://www.cplusplus.com/forum/general/37874/#msg203487

[caneta]

Thank you.

But is there a solution that not involves boost libraries?

[kbw]

You can make up your own variant. If you know the types are (you already said int, float, string) you can just support those.
http://www.cplusplus.com/forum/general/36365/#msg199469

[m4ster r0shi]

caneta wrote:

I'm wondering if it's possible to do something like that with inheritance...

It is. The idea is to have an abstract Flag class and derive a templated class from it.

class BaseFlag {/*...*/};

template <class T>
class Flag : public BaseFlag {/*...*/};

Then, you can do something like this:

vector<BaseFlag*> cmdLineVect;

cmdLineVect.push_back(new Flag<int>(-12));
cmdLineVect.push_back(new Flag<double>(5.5));
cmdLineVect.push_back(new Flag<char>('d'));
//etc... 

caneta wrote:

But is there a solution that not involves boost libraries?

Yes. Check this out -> http://www.cplusplus.com/forum/general/33247/

EDIT: Fixed a horrible syntax error...

[caneta]

I'm getting creazy, trying to create a minimal example with boost.
Here's what I have implemented:

#include <iostream>
#include <vector>
#include <boost/variant.hpp>

using namespace std;
using namespace boost;

template <class T>
class B
{
	T value;

	public:
	B(T v) { value = v; };
	T getValue() { return value; }
};

typedef variant<B<int>, B<float>, B<double>, B<string> > var_t;

class print_visitor : boost::static_visitor<>
{
	public:
		template<typename T>
			void operator()(T & x) const
			{
				cout << "Print something" << endl;
			}
};

class A
{
	vector<var_t> vec;

	public:
	void addObj(var_t obj) { vec.push_back(obj); }
	var_t getObj(int i) { return vec.at(i); }
};

int main(int argc, char* argv[])
{
	A *container = new A();

	B<int>    elem1(10);

	container->addObj(elem1);

	apply_visitor( print_visitor(), container->getObj(0) );

	return 0;
}

...and here the compilation error:

heterogeneousContainerBoost.cpp: In function ‘int main(int, char**)’:
heterogeneousContainerBoost.cpp:52: error: no matching function for call to ‘apply_visitor(print_visitor, var_t)’
/usr/include/boost/variant/detail/apply_visitor_unary.hpp:54: note: candidates are: typename Visitor::result_type boost::apply_visitor(Visitor&, Visitable&) [with Visitor = print_visitor, Visitable = var_t]
/usr/include/boost/variant/detail/apply_visitor_unary.hpp:70: note:                 typename Visitor::result_type boost::apply_visitor(const Visitor&, Visitable&) [with Visitor = print_visitor, Visitable = var_t]

I don't understand where I am wrong...can you help me?