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[CLJ-2] Scopes Created: 15/Jun/09  Updated: 15/May/17

Status: Open
Project: Clojure
Component/s: None
Affects Version/s: None
Fix Version/s: None

Type: Feature Priority: Major
Reporter: Assembla Importer Assignee: Rich Hickey
Resolution: Unresolved Votes: 2
Labels: None

Attachments: Text File scopes-spike.patch    


Add the scope system for dealing with resource lifetime management

Comment by Assembla Importer [ 24/Aug/10 11:43 AM ]

Converted from http://www.assembla.com/spaces/clojure/tickets/2

Comment by Assembla Importer [ 24/Aug/10 11:43 AM ]

richhickey said: Updating tickets (#8, #42, #113, #2, #20, #94, #96, #104, #119, #124, #127, #149, #162)

Comment by Stuart Halloway [ 12/Jul/11 8:26 AM ]

Patch demonstrates idea, not ready for prime time.

Comment by Tassilo Horn [ 23/Dec/11 7:37 AM ]

I think the decision of having to specify either a Closeable resource or a close function for an existing non-Closeable resource in with-open is quite awkward, because they have completely different meaning.

  (let [foo (open-my-custom-resource "foo.bar")]
    (with-open [r (reader "foo.txt")
                foo #(.terminate foo)]
      (do-stuff r foo)))

I think a CloseableResource protocol that can be extended to custom types as implemented in the patch to CLJ-308 is somewhat easier to use. Extend it once, and then you can use open-my-custom-resource in with-open just like reader/writer and friends...

That said, Scopes can still be useful, but I'd vote for handling the "how should that resource be closed" question by a protocol. Then the with-open helper can simply add

(swap! *scope* conj (fn [] (clojure.core.protocols/close ~(bindings 0))))

and cleanup-scope only needs to apply each fn without having to distinguish Closeables from fns.

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