On Friday, 1 May 2015 at 11:20:32 UTC, Chris wrote:
On Friday, 1 May 2015 at 11:11:28 UTC, biozic wrote:
On Friday, 1 May 2015 at 11:01:29 UTC, Chris wrote:


Thinking about it,

T factory(T)() {
return T();
}

is better suited for a factory (with static type checks).

But then I don't know what factory!X() provides that X() alone doesn't.

Just cleaner code with type checks

T factory(T)() {
  static if (is (T == A)
              || (is (T == B)))
    return T();
  else
    assert(0, "Type "~T.stringof~" is not supported");
}

and then you could have

auto getType(string type = "")() {
  static if (type == "A")
    return factory!A();
  else static if (type == "B")
    return factroy!B();
  else
    return factory!A();  // default
}

in order to separate the logic, i.e. the factory produces the type and performs all the type checks, whereas `getType` is the interface for the user.

A "factory" that produces a *type* could be:
--
template checked(T) {
    static if (is (T == A) || (is (T == B)))
      alias checked = T;
    else
      static assert(0, "Type "~T.stringof~" is not supported");
}
--

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