Serialization/deserialization of templated class

[Jacob Carlborg via Digitalmars-d]

On 2017-06-28 07:52, Dmitry Solomennikov wrote:
> On Wednesday, 28 June 2017 at 05:01:17 UTC, Eugene Wissner wrote:
>> On Wednesday, 28 June 2017 at 04:41:25 UTC, Dmitry Solomennikov wrote:
>
>
>> Probably if you have serialized data, you convert strings to other
>> types, so it may be possible to perfom if-checks:
>> if (myDataIsStringAndDouble(data))
>> {
>>   auto var = new Some!(Pair!(string, double))(new Pair!(string,
>> double)("df", 5.0));
>> }
>> else if (myDataIsStringAndInt(data))
>> {
>>   auto var = new Some!(Pair!(string, int))(new Pair!(string,
>> int)("df", 5));
>> }
>
> It is possible, but it is not a general solution. I've posted couple of
> sample classes, but there are more complicated cases, of course, and it
> well be combinatorial explosion here.
>
> I got the Variant idea, I'll give it a try.
>  From other point of view, is there a reflection, say
>
> auto i = newInstance("Pair!(int, string)(10, \"asdf\")"),
>
> something like in Java?

It's possible to instantiate classes using reflection in D, but not for 
templated classes:

class Foo(T) {}
class Bar {}

void main()
{
     Foo!int a = new Foo!int;
     Bar b = new Bar;

     auto o1 = Object.factory("main.Foo!int.Foo"); // does not work for 
templated classes
     auto o2 = Object.factory("main.Bar"); // works for non-templated 
classes

     assert(o1 is null);
     assert(o2 !is null);
}

Actually, if you have the template instantiation available you can do this:

Object o = Foo!int.classinfo.create();

-- 
/Jacob Carlborg