Great! Many thanks.
Dave
On Sunday, 17 March 2013 08:18:27 UTC, dennis wrote:
>
> Sorry,it's getDeclaredConstructor:
>
> (-> klassname (Class/forName) (. getDeclaredConstructor String int)
> (.newInstance host port))
>
>
> 2013/3/17 dennis zhuang <killm...@gmail.com <javascript:>>
>
>> You can get the constructor and instance it:
>>
>> (-> klassname (Class/forName) (.getDeclaredConstructors String int)
>> (.newInstance host port))
>>
>>
>> 2013/3/17 Dave Snowdon <dave.s...@gmail.com <javascript:>>
>>
>>> I need the ability to create one of a number of java classes which have
>>> constructors taking a known list of parameters. There are a large enough
>>> number of classes that having a set of conditions testing for each class
>>> name would be unmanageable. The classes are from a third-party jar file so
>>> I cannot modify them either.
>>>
>>> The trouble is that new is special form and does not evaluate it's first
>>> parameter so if I write an expression like
>>> (new (Class/forName klassname) param1 param2) it fails
>>> because (Class/forName klassname) is treated as the class name rather than
>>> being evaluated first.
>>>
>>> The closest I've got so far is to write the following macro
>>>
>>> (defmacro make-proxy
>>> "Build proxy class from name and map"
>>> [klassname params] (list 'new (Class/forName klassname) '(:hostname
>>> params) '(:port params)))
>>>
>>> This gets me some of the way, I can now write
>>> (make-proxy "com.example.foo" {:hostname "127.0.0.1 :port 9559})
>>> but it only works for constant strings since the first parameter is
>>> evaluated when the macro is expanded.
>>>
>>> Can anyone suggest a solution?
>>>
>>> thanks
>>>
>>> Dave
>>>
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>>>
>>
>>
>>
>> --
>> 庄晓丹
>> Email: killm...@gmail.com <javascript:> xzh...@avos.com<javascript:>
>> Site: http://fnil.net
>> Twitter: @killme2008
>>
>>
>>
>
>
> --
> 庄晓丹
> Email: killm...@gmail.com <javascript:> xzh...@avos.com<javascript:>
> Site: http://fnil.net
> Twitter: @killme2008
>
>
>
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