What's the benefit to writing code like this? The only thing I could possibly see as being considered an advantage is that it encapsulates the file channel, but you've exposed that via a key anyway.
- James On 21 November 2015 at 02:54, William la Forge <laforg...@gmail.com> wrote: > Code as data is the mantra. Functions and closures as data. So why not > objects as data? What I propose is nothing new, but perhaps a new style. > > Making objects from map structures is simple enough in Clojure. And easy > enough to put functions in a map. So why not closures? A closure in a map > is a lot like an object method, hmm? > > I found clojure components to be inspirational. But as light-weight as > they are, components are still too heavy-weight to be objects. But a simple > map seems ideal. And with only a map instead of a record or deftype, > composition is simplicity itself. But the key idea here comes from clojure > components: contents of the map should be configuration parameters or > architecture, but not state. Put state in an atom and then (optionally) put > the atom in the map. But once an object is formed, the contents of the map > should not change. There should be no need to update a reference to this > map. > > Below is what I am calling a Clojure Object. Like a Java object, the > method holds both data and methods (closures). Note that, because we are > using closures, local data can be accessed without having to be put in the > map. For example, the file-channel variable is not accessed via the map and > need not have been added to the map. > > Bill > > (ns aatree.db-file > (:require [clojure.tools.logging :as log]) > (:import (java.nio.channels FileChannel) > (java.nio.file OpenOption StandardOpenOption))) > > (defn db-file-open > ([file opts] > (db-file-open (assoc opts :db-file file))) > ([opts] > (if (not (:db-file opts)) > (throw (Exception. "missing :db-file option"))) > (let [file (:db-file opts) > ^FileChannel file-channel > (FileChannel/open (.toPath file) > (into-array OpenOption > [StandardOpenOption/CREATE > StandardOpenOption/READ > StandardOpenOption/WRITE])) > opts (assoc opts :db-file-channel file-channel) > opts (assoc opts > :db-close > (fn [] > (try > (.close file-channel) > (catch Exception e > (log/warn e "exception on close of db-file"))) > (dissoc opts :db-file-channel))) > opts (assoc opts > :db-file-empty? > (fn [] > (= 0 (.size file-channel)))) > opts (assoc opts > :db-file-read > (fn [byte-buffer position] > (.read file-channel byte-buffer position))) > opts (assoc opts > :db-file-write > (fn [byte-buffer position] > (.write file-channel byte-buffer position))) > opts (assoc opts > :db-file-write-root > (fn [byte-buffer position] > (.force file-channel true) > (.write file-channel byte-buffer position) > (.force file-channel true))) > opts (assoc opts > :db-file-force > (fn [] > (.force file-channel true)))] > opts))) > > -- > 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 > --- > You received this message because you are subscribed to the Google Groups > "Clojure" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to clojure+unsubscr...@googlegroups.com. > For more options, visit https://groups.google.com/d/optout. > -- 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 --- You received this message because you are subscribed to the Google Groups "Clojure" group. To unsubscribe from this group and stop receiving emails from it, send an email to clojure+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
