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digitalmars.D - Complex Object Generation with Templates/Mixins

reply Chris Williams <littleratblue yahoo.co.jp> writes:
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.
Jun 02 2009
parent reply Jarrett Billingsley <jarrett.billingsley gmail.com> writes:
On Tue, Jun 2, 2009 at 12:03 PM, Chris Williams
<littleratblue 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 uns=

 template ClassGen(char[] className, char[][][] classMembers) {
 =A0 const char[] ClassGen =3D "class " ~ className ~ " {";
 =A0 for (int i =3D 0; i < classMembers.length; i++) {
 =A0 =A0 =A0classGen ~=3D classMembers[i][0] ~ " " ~ classMembers[i][1] ~ =

 =A0 }
 =A0 classGen ~=3D "}";
 }

 mixin(
 =A0 ClassGen!(
 =A0 =A0 =A0"Foo",
 =A0 =A0 =A0[
 =A0 =A0 =A0 =A0 ["int", "bar"],
 =A0 =A0 =A0 =A0 ["int", "baz"]
 =A0 =A0 =A0]
 =A0 )
 );

 It seems like somehow between templates, mixins, and tuples (tuple arrays=

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 =3D "class " ~ className ~ " {"; foreach(member; classMembers) ret ~=3D 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.
Jun 02 2009
parent Chris Williams <littleratblue yahoo.co.jp> writes:
Jarrett Billingsley Wrote:
 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.

Wonderful. Thank you.
Jun 02 2009