infer type argument in classe constructor?

[Simen Kjaeraas via Digitalmars-d-learn]

On Tuesday, 29 March 2016 at 10:13:28 UTC, Puming wrote:
> Hi,
>
> I'm writing a generic class：
>
> ```d
>
> struct Message { ... }
>
> class Decoder(MsgSrc) {
> }
> ```
>
> When using it, I'd have to include the type of its argument:
>
> ```
> void main() {
>    Message[] src = ...;
>
>    auto decoder = new Decoder!(Message[])(src);
>
>    ...
> }
> ```
>
> Can it be inferred so that I only need to write?
>
> ```d
> auto decoder = new Decoder(src); // you can infer the type from 
> src.
> ```

Nope. To see why, consider a class like this:

class A(T) {
   T data;
   this(int n) {
   }
}

void main() {
    auto a = new A(3); // What is T?
}

The common solution is a simple 'create' function:

Decoder!T decoder(T)(T msg) {
     return new Decoder!T(msg);
}

--
   Simen