Not 100% on this, but this is what I do when reading files...
(with-open [rdr (BufferedReader. (FileReader. file-name))]
(reduce conj [] (line-seq rdr)))
That ensures that the whole seq is realized without closing the
handle, but it also allows you to wrap the whole block with a take
function if you only cared about the first few lines. As far as I
know, this would still close the resources after whether you realize
the whole sequence or only take part of it. Can someone who knows a
bit better confirm?
On Aug 3, 5:28 pm, Jeff Palmucci <jpalmu...@gmail.com> wrote:
> See my library athttp://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 <dammi...@gmail.com> 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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