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cljc.java-time

A Clojure(Script) library which mirrors the java.time api through kebab-case-named vars.

It also has predicates for each entity: (cljc.java-time.extn.predicates/instant? x)

See my talk at Clojure/North 2019 for more background.

This library also works on babashka

Related Libraries

tick is a higher level date-time library that uses this one. Even if you're using cljc.java-time directly, ie not through tick, it has very relevant docs on extra setup for use with ClojureScript

time-literals is a Clojure(Script) library which provides tagged literals for objects from jsr-310 domain

Rationale

This library sits atop java.time on the jvm and cljs.java-time on Javascript platforms. Writing cross-platform code that uses those libraries directly is harder than interop normally is because:

  • To call the java.time 'static' methods in a cljc file you need to use the dot-special-form which is not idiomatic
  • The underlying js library has changed the name of the getter methods in java.time (in almost all cases) to remove the 'get' part of the name. There are ways to get around that on a case by case basis, but this library handles it for you.

How it works

For every class in java.time, there is a clojure namespace.

For example, corresponding to java.time.LocalDate, there is a namespace

cljc.java-time.local-date

In that and every other namespace, there is one var per public method/field in the corresponding class.

For example, for the method java.time.LocalDate/parse, there is a corresponding function cljc.java-time.local-date/parse

Instance methods take the instance as the extra first arg

Usage

Get it from Clojars

Version 0.1.9 and up require minimum Clojurescript version of 1.10.741

In .cljc file

(ns my.cljc
  (:require  [cljc.java-time.local-date :as ld])
  
  ;create a date
  (def a-date (ld/parse "2019-01-01"))
  
  ;add some days
  (ld/plus-days a-date 99)
  

Problems & Irregularities

java.time.Year#isLeap exists as an instance method and a static method. Only the static version has been wrapped.

Inheritcance/Polymorphism

The code of this project consists of mechanically generated functions for the java.time methods, even if those methods are inherited via superclasses or interfaces. In this project, functions are generated in every class they can be applied to. For example there is cljc.java-time.temporal.temporal/is-supported and also cljc.java-time.local-date/is-supported, with the latter being essentially unnecessary but included anyway.

Note

Java 9

New methods were added in Java 9 - these are not included in this library

ClojureScript

Be aware that the underlying js implementation is probably only 99% complete. Anything you find missing can be added via pull request to js-joda

License

Copyright © 2020 Widd Industries

Distributed under the Eclipse Public License either version 1.0 or (at your option) any later version.

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Henry Widd & Alan Thompson
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