templates in a std::vector??

[Bart Kevelham]

Hi all,

I have the following problem
I need to store a list of simple objects. The general form of these
objects is:
- std::string type
- std::string name
- value

The problem lies within the value. This can be of any type. A
std::string or an openGL float4 or whatever. This could easily be
implemented with a template, but the problem is this: I have to store
instances of this object in something like a stl vector or list
(Anything that is growable). So the final list can contain one instance
whose value is a string and another instance whose value is an integer
(for example). I can't figure out a way to do this. Does anyone of you
guys/girls have an idea?

Kind regards,

Bart

 

[Thomas Maier-Komor]

Hi all,

I have the following problem
I need to store a list of simple objects. The general form of these
objects is:
- std::string type
- std::string name
- value

The problem lies within the value. This can be of any type. A
std::string or an openGL float4 or whatever. This could easily be
implemented with a template, but the problem is this: I have to store
instances of this object in something like a stl vector or list
(Anything that is growable). So the final list can contain one instance
whose value is a string and another instance whose value is an integer
(for example). I can't figure out a way to do this. Does anyone of you
guys/girls have an idea?

Kind regards,

Bart

make a class B with type and name and derive from it for the different
value types. Then instead of using a vector<B>, use a vector<B *>.
Remember that you cannot store objects of different size within
a vector, which also effectively disables assigning a derivation of B
to an element of a vector<B>, as only the B part will be assigned
omitting the extensions made during derivation...

 

[John Harrison]

Hi all,

I have the following problem
I need to store a list of simple objects. The general form of these
objects is:
- std::string type
- std::string name
- value

The problem lies within the value. This can be of any type. A
std::string or an openGL float4 or whatever. This could easily be
implemented with a template, but the problem is this: I have to store
instances of this object in something like a stl vector or list
(Anything that is growable). So the final list can contain one instance
whose value is a string and another instance whose value is an integer
(for example). I can't figure out a way to do this. Does anyone of you
guys/girls have an idea?

Kind regards,

Bart

Thomas' suggestion is one way to go. The other is to use a class that has
been written to hold a variety of types. Implementing this is tricky but
fortunately its already been done for you. Check out the boost::any class
http://www.boost.org/doc/html/any.html and the boost::variant class
http://www.boost.org/doc/html/variant.html

john

 

[Bart Kevelham]

Thomas' suggestion is one way to go. The other is to use a class that has

been written to hold a variety of types. Implementing this is tricky but
fortunately its already been done for you. Check out the boost::any class
http://www.boost.org/doc/html/any.html and the boost::variant class
http://www.boost.org/doc/html/variant.html

Hey cool, I didn't know about that. Boost keeps amazing me.

Thanks (and also a "thank you" for Thomas of course),

Bart

 

[Brian Riis]

Hey cool, I didn't know about that. Boost keeps amazing me.

Thanks (and also a "thank you" for Thomas of course),

Bart

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