The `new` reader macro must resolve its first argument at compile time.
That's why (new (symbol s)) doesn't work.
Thanks,
Ambrose
On Wed, Aug 6, 2014 at 6:55 PM, Colin Yates <colin.ya...@gmail.com> wrote:
> Ah OK, I didn't realise I needed to get into Java interop.
>
> For education - can you (or anyone) explain me as to why what I was trying
> didn't work?
>
> Thanks Ambrose.
>
>
> On 6 August 2014 11:50, Ambrose Bonnaire-Sergeant <
> abonnaireserge...@gmail.com> wrote:
>
>> Hi Colin,
>>
>> If you must call the Java constructor, you need reflection.
>>
>> user=> (defrecord B [c])
>> user.B
>> user=> (def s "user.B")
>> #'user/s
>> user=> (.newInstance (first (.getDeclaredConstructors (Class/forName s)))
>> (object-array [1]))
>> #user.B{:c 1}
>>
>> Thanks,
>> Ambrose
>>
>>
>> On Wed, Aug 6, 2014 at 6:37 PM, Colin Yates <colin.ya...@gmail.com>
>> wrote:
>>
>>> Hi,
>>>
>>> tldr; if I have a (defrecord MyRecord) in ns a.b.c and I have a string
>>> "a.b.c.MyRecord" how I can invoke (a.b.c.MyRecord.) (or (new
>>> a.b.c.MyRecord)?
>>>
>>> I thought this was going to be as simple as (defn cfn "a.b.c.MyRecord")
>>> ((symbol cfn).) but that throws an ArityException: wrong number of args (0)
>>> passed to Symbol. I
>>>
>>> I have a protocol with a number of implementations. Each installation
>>> will have a single implementation and will chose one based on an
>>> environment variable. At runtime I need to look at that environment
>>> variable which defines the fully qualified implementation of a protocol. I
>>> then need to instantiate that record.
>>>
>>> Architecturally equivalent to a simple plugin system. I could alias
>>> them all but that requires knowing about all the implementations which is a
>>> no-go.
>>>
>>> This is where I feel the pain of not having OSGi :).
>>>
>>> Thanks all!
>>>
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