On Tuesday, 12 November 2013 at 23:47:10 UTC, Andrei Alexandrescu
wrote:
On 11/12/13 3:05 PM, Jakob Ovrum wrote:
On Tuesday, 12 November 2013 at 22:36:22 UTC, Timon Gehr wrote:
- Every class in any imported module will need to show up in
the
generated code even if it is never used unless global static
analysis
is carried out on arguments to Object.factory.
- If I know the fully qualified name of a class, there are
better ways
to instantiate this class than passing a string containing
that name
to Object.factory in order to call the default constructor.
- The functionality provided by Object.factory is trivially
replaced
by a solution more specifically tailored to the problem at
hand using
compile-time reflection.
+ 1.
To test, I made a Factory template that works like this:
---
unittest
{
import std.traits : fullyQualifiedName;
interface I {}
class A : I {}
class B : I {}
alias f = Factory!(I, A, B);
Stopped reading here, and everybody should. There is a thorough
treatment of object factories in "Modern C++ Design" which I
recommend not because I wrote it, but because it's thorough.
Part of it is to show why the approach above is marred by
dependency issues and should often be avoided.
Sure, it has dependency issues, it needs to know all the types
then and there, with is the anti-thesis of many factories. So,
call it something else, like TypeMap, and it's still a useful
type.
But alright, it is not a good factory.
