(def m (fun-map {:a (future (+ 5 3))}))
(:a m) ;=> 8Liking cljdoc? Tell your friends :D
fun-map, a data structure blurs the line between identity, state and function
Fun-map is a Clojure(Script) map data structure. The difference between it and a normal map is: the values are evaluated until you take the value of it.
Usage scenarios
as a lazy map
If you put a clojure.lang.IDeRef instance like a deferred value (created by defer) or future into the map, deref will be automatically called when you access it. This way, the map can be thought of as a lazy map.
You can specify :keep-ref to disable this default feature, and use fnk to force it to be lazy for individual values.
|
dependent injection
Your values can now depend on the map itself, most commonly on other values.
(def m
(fun-map {:numbers (range 10)
:cnt (fnk [numbers] (count numbers))
:sum (fnk [numbers] (apply + numbers))
:average (fnk [cnt sum] (/ sum cnt))}))This feature is similar to Plumatic Plumbing’s graph, it even has the same name fnk macro! The difference is that fun-map is a normal map, you could update the values (and the fnk function) at any time. You could use a plain map if you want to test some complex computations.
lifecycle management
A fun-map can track the realization order of its values by specifying a :trace-fn option, combine this and the dependency injection nature, leads to a simple lifecycle management feature.
life-cycle-map is a fun-map that can orderly close your lifecycle components.
(def system
(life-cycle-map
{:component/a
(fnk []
(closeable 100 #(println "halt :a"))) (1)
:component/b
(fnk [:component/a]
(closeable (inc a) #(println "halt :b")))}))
(touch system) (2)
(halt! system) (3)| 1 | closeable function turns a value to a closeable value, the specified close function will be called when the whole system is being close. |
| 2 | touch travels the system, and makes potential lazy values realized, in a real application, you may not want to do it. |
| 3 | halt! is a function that closes a closeable value. |
Example
Waterfall library uses life-cycle-map to do dependency injection and lifecycle management, turns Kafka usage into map accessing.
API
The complete API documents are on cljdocs.
Some of the most frequently used APIs are:
-
fun-map -
fnk(macro) -
fw(macro)
(defn book-of
[connection author]
(-> (fun-map {:datomic/db (fnk [:datomic/connection] (d/db connection)) (1)
:books (fnk [:datomic/db author]
(d/q '[:find ?e
:in $ ?name
:where [?e :book/author ?name]]
db author))
:book-count (fnk [books] (count books))})
(assoc :datomic/connection connection :author author))) (2)
(book-system (d/connect "datomic:mem://books") "Harry Potter")| 1 | fnk accepts namespaced keywords. |
| 2 | by assoc key-value pairs to a fun-map, you turn Datomic API into a map. |
Development
Fun-map using kaocha as the test runner.
-
use
clj -M:test --watchto automatically run tests whenever code changes.
License
Copyright © 2018, 2019, 2022 Robertluo
Distributed under the Eclipse Public License either version 1.0 or (at your option) any later version.
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