Hello,
I can't find a solution to a polymorphic problem. I construct a system
to compute a value but I want it to be generic so it doesn't have to
know on what type it computes.
So I use generic and it works fine. Now the system store the object on
what it computes in a collection ([]). The object are stored them computed.
I've done a sample code :
pub trait Base {
fn do_base(&self);
}
struct TestBase;
impl Base for TestBase {
fn do_base(&self) {
println!("ici");
}
}
trait GenerciFn {
fn do_generic<T: Base>(&self, base: &T);
}
struct DoGenericFn;
impl GenerciFn for DoGenericFn {
fn do_generic<T: Base>(&self, base: &T) {
base.do_base();
}
}
struct ToTestStr {
vec_gen: ~[~TestBase],
}
impl ToTestStr {
fn testgencall<T: GenerciFn>(&self, gen: &T) {
for base in self.vec_gen.iter() {
//let test = base as &~TestBase;
gen.do_generic(&**base);
}
}
}
#[main]
fn main() {
let base = TestBase;
let test = ToTestStr {vec_gen: ~[~base],};
let gen = DoGenericFn;
test.testgencall(&gen);
}
This code work but I would like to replace the vec_gen: ~[~TestBase],
with vec_gen: ~[~Base].
I didn't find a solution. I'am not shure it's possible because it's
sort of dynamic polymorphism that it's very hard to do at compile time.
How the compiler know that my collection contains TestBase.
I think I don't use the right way to do this in Rust. Perhaps I'am too
used to dynamic polymorphic language like Java, C#, .... What I want is
that my lib doesn't know the real Base type use but the user's lib knows
and tell by adding the right type to a collection.
Philippe Delrieu
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