Array/collection of templated class

[Chris Nicholson-Sauls]

Hasan Aljudy wrote:
> Chris Nicholson-Sauls wrote:
> 
>> I'm working on a project of mine, and I came across this little 
>> problem.  Now, it may well be that the solution is staring me in the 
>> face, but I just can't seem to come up with a feasible solution to 
>> this: I can't have an array of a templated class.
>>
>> To illustrate:
>>
>> ########## foo.d
>> # class Foo (T) {
>> #   public this (T a_value) { p_value = a_value; }
>> #
>> #   public T value () { return p_value; }
>> #   private T p_value;
>> # }
>> #
>> # void main () {
>> #   Foo[] arr;
>> # }
>>
>> This will give the error:
>> foo.d(9): class foo.Foo(T) is used as a type
>>
>> Now, granted, I expected this.  But I'm at a loss as to what to do.  
>> Sure, if I had a way of knowing the signatures of the template 
>> instances I could just use "Object[]" decleration and a cast() 
>> expression on the lookup, but this is for a system where I usually 
>> won't know.
>>
>> Ideas?
>>
>> -- Chris Nicholson-Sauls
> 
> 
> Hmm .. templates are generally used for things that you know at compile 
> time, if you don't, well .. trying doing something different.

The reason I won't know, is because the template instances are built and made available by 
various objects, independantly of each other.  Consider this contrived example:

########## module somelib.d
# class Foo (T) {
#   public this (char[] a_name, T* a_what) {
#     p_name = a_name ;
#     p_what = a_what ;
#   }
#
#   public char[] name  () { return p_name  ; }
#   public T      value () { return *p_what ; }
#
#   private char[] p_name;
#   private T*     p_what;
# }
#
# class Bar {
#   package int p_alpha ,
#               p_beta  ;
#
#   public Foo[] wrap () {
#     Foo[] result;
#     result ~= new Foo!(int)(
#   }
#
#   public int doStuff () { /* ... */ }
# }

########## module someapp.d
# import std.stdio ;
# import somelib   ;
#
# void main () {
#   Bar   mybar = new Bar    ;
#   Foo[] wbar  = mybar.wrap ;
#
#   while (mybar.doStuff)
#     foreach (x; wbar)
#       writefln("%s(%s)", x.name, x.value);
# }

-- Chris Nicholson-Sauls