Re: templating

[klaus triendl <klaus triendl eu>]

Robert Rehammar schrieb:
> class myNodeClass : NodeTree<tClass> {
> 	myNodeClass (string s) :
> 		NodeTree<tClass> {
> 		...
> 	};
> }

You forgot the parentheses:

 	myNodeClass (string s) :
 		NodeTree<tClass>() {
 		...
 	};


> But this won't compile as the template for NodeTree, tClass, requires a
> parameter (the string s) and I simply can't figure out how to pass it to
> the template.
>
> Writing the constructor as
>
> myNodeTree (string s): NodeTree<tClass (s)> won't compile, complaining
> that s can't appear in a constant expression, so this seem so suggest
> that I can't template with a class that require any parameters for
> initiation...

You don't want to pass a parameter to a class at compile time but at 
runtime.
I assume that NodeTree is the Glib::NodeTree<> template class. It takes 
a *compile time* parameter T which is your class tClass. You want to 
pass it a *runtime parameter* when it gets constructed while the program 
is executing. So you have to know what NodeTree<> does with its template 
parameter T. Looking at NodeTree's declaration you will find an explicit 
constructor: explicit NodeTree(const T& data).
This means that you can pass NodeTree's constructor a tClass object 
which in turn you can construct with the string like so:

class myNodeClass: NodeTree<tClass>
{
  // better take a const reference to avoid string copying
  myNodeClass(const string& s):
    NodeTree<tClass>(tClass(s))
  {
    // ...
  }
};



Klaus