subwatch

A Clojure library designed to make watching parts of a datastructure in an atom easier.

I'm not sure if this whole nested atom thing is a good idea or not but I'm going to find out.

Installation

Add the following to the dependencies in your project.clj:

[subwatch "1.0.0"]

Usage

Require it in the REPL:

(require '[subwatch.core :as subwatch])

Require it in your application:

(ns my-app.core
  (:require [subwatch.core :as subwatch]))

Assuming the following atom:

(def my-atom {:a {:b {:c {:d 4}
                      :e 5}}})

You can watch just the :d key for changes:

(defn report-sum! [val]
    (println "Sum " (+ (get-in val [:a :b :c :d])
                       (get-in val [:a :b :c :e]))))

(add-sub-watch my-atom ::my-key [:a :b :c :d] report-sum!)

(swap! my-atom #(assoc-in % [:a :new-key] 5150))
;; Nothing is printed because it's outside the desired scope

(swap! my-atom #(assoc-in % [:a :b :c :d] 2112))
;; Prints "Sum 2117" because it is inside the desired scope.

And of course remove the sub-watch later:

(remove-sub-watch my-atom ::my-key)

License

This library is in the public domain.