On Mon, Jun 15, 2009 at 9:13 AM, Parth<parth.malwan...@gmail.com> wrote:
>
>
>
> On Jun 15, 7:08 am, James Koppel <darmanith...@gmail.com> wrote:
>> I am trying to write a function to simplify working with GridBagConstraints
>> -- that is, instead of writing
>>
>> (let [c (GridBagConstraints.)]
>> (set! (.weightx c) 2.0)
>> (set! (.gridwidth c) GridBagConstraints/REMAINDER)
>> (let [button (JButton. "Hello, world!")]
>> (.setConstraints (.getLayout *my-container*) button c)
>> (.add *my-container* button)))
>>
>> I could simply write
>>
>> (gridbag-add *my-container*
>> (JButton. "Hello, world!")
>> "weightx=2.0;gridwith=GridBagConstraints/REMAINDER")
>>
>> A simple combination of regexes and read-string would easily allow me to
>> extract the symbol 'GridBagConstraints/REMAINDER from the example string,
>> but I'm having trouble actually converting it into its value. Using resolve
>> simply returns nil, and getting "." to work dynamically seems to be
>> fruitless, as even this simple call
>>
>> (. (resolve 'GridBagConstraints) REMAINDER)
>>
>> throws an exception.
>>
>> So, the question is, how do I go dynamically from a string like
>> "GridBagConstraints/REMAINDER" to the actual value of the static field?
>>
>> Of course, eval does the trick, but I'd rather not have to resort to it.
>
> One way to do that would be to use a map:
>
> user=> (def m {"Math/PI" Math/PI "Math/E" Math/E})
> #'user/m
> user=> (defn foo [n s] [n (get m s :not-found)])
> #'user/foo
> user=> (foo 10 "Math/PI")
> [10 3.141592653589793]
> user=>
>
> You could also consider writing a function that takes these
> as parameters and returns the updated container. That way
> you can avoid the regex.
>
> Regards,
> Parth
>
Not sure if this can be fit in with what you're trying to do, but you
can accomplish this with a macro:
user=> (defmacro resolve-sym-str [s] (let [[ns sym] (.split s "/")]
(symbol ns sym)))
#'user/resolve-sym-str
user=> (resolve-sym-str "Math/PI")
3.141592653589793
user=>
However, looking at this further, it seems that the first part of what
you have tried works:
user=> (import '(java.awt GridBagConstraints))
nil
user=> (resolve 'GridBagConstraints)
java.awt.GridBagConstraints
Now you can use Java's reflection API to grab the field you want:
user=> (-> (resolve 'GridBagConstraints) (.getDeclaredField
"REMAINDER") (.get nil))
0
So it would appear this is possible without a macro, which probably
makes it easier to use.
/mike
--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google
Groups "Clojure" group.
To post to this group, send email to clojure@googlegroups.com
Note that posts from new members are moderated - please be patient with your
first post.
To unsubscribe from this group, send email to
clojure+unsubscr...@googlegroups.com
For more options, visit this group at
http://groups.google.com/group/clojure?hl=en
-~----------~----~----~----~------~----~------~--~---
