See my library at http://github.com/jpalmucci/clj-yield, which makes
this trivial.
For example, here is a function I use to read a sequence of java
serialized objects from a stream:
(defn read-objects [path]
(with-yielding [out 1000]
(with-open [stream (java.io.ObjectInputStream.
(java.io.BufferedInputStream.
(java.util.zip.GZIPInputStream.
(java.io.FileInputStream. (io/file path)))))]
(loop []
(try
(let [next (.readObject stream)]
(yield out next)
(recur))
(catch java.io.EOFException e (.close stream)))))))
When the sequence returned by with-yielding becomes garbage
collectable, yield will throw an exception causing with-open to close
the file.
Note that with-yielding will use a thread from the thread pool, so its
a bad idea to have hundreds of active with-yieldings at once.
On Aug 3, 3:21 pm, David Andrews <[email protected]> wrote:
> I want to create a lazy seq backed by an open file (or db connection,
> or something else that needs cleanup). I can't wrap the consumer in a
> with-anything.
>
> Is there a general method for cleaning up after the consumer discards
> its reference to that lazy seq? I'm vaguely aware of Java finalize,
> but am also aware that it is unpredictable (e.g. you aren't guaranteed
> to be driven at the next gc).
>
> Does Clojure even provide the ability to define a finalize method for
> a lazy seq?
>
> (Sipping water from a firehose...)
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