Complex Object Generation with Templates/Mixins

[Jarrett Billingsley]

On Tue, Jun 2, 2009 at 12:03 PM, Chris Williams
<littleratblue at yahoo.co.jp> wrote:
> I would like to do something similar to the example at:
>
> http://www.digitalmars.com/d/1.0/mixin.html
>
> I want to create a class dynamically, but I want to be able to add an unspecified number of items to it. Pseudo-code, but something like this:
>
> template ClassGen(char[] className, char[][][] classMembers) {
>   const char[] ClassGen = "class " ~ className ~ " {";
>   for (int i = 0; i < classMembers.length; i++) {
>      classGen ~= classMembers[i][0] ~ " " ~ classMembers[i][1] ~ ";"
>   }
>   classGen ~= "}";
> }
>
> mixin(
>   ClassGen!(
>      "Foo",
>      [
>         ["int", "bar"],
>         ["int", "baz"]
>      ]
>   )
> );
>
> It seems like somehow between templates, mixins, and tuples (tuple arrays?) that something like this should be possible, but I'm still figuring out the language.

You'll be happy to know that your code compiles and works with very
little modification.

char[] ClassGen(char[] className, char[][][] classMembers) {
  char[] ret = "class " ~ className ~ " {";
  foreach(member; classMembers)
     ret ~= member[0] ~ " " ~ member[1] ~ ";";

  return ret ~ "}";
}

mixin(
  ClassGen(
     "Foo",
     [
        ["int", "bar"],
        ["int", "baz"]
     ]
  )
);

You can't use for loops in templates, so instead you have to use
recursion.  In this case, however, a CTFE function is much terser.