secretary

A client-side router for ClojureScript.

Contents

• Installation
• Guide
  • Basic routing and dispatch
  • Route matchers
  • Parameter destructuring
  • Query parameters
  • Named routes
• Example with history
• Available protocols
• Contributors
• Committers

Installation

Add secretary to your project.clj :dependencies vector:

[clj-commons/secretary "1.2.4"]

For the current SNAPSHOT version use:

[clj-commons/secretary "1.2.5-SNAPSHOT"]

Guide

To get started :require secretary somewhere in your project.

(ns app.routes
  (:require [secretary.core :as secretary :refer-macros [defroute]]))

Note: starting ClojureScript v0.0-2371, :refer cannot be used to import macros into your project anymore. The proper way to do it is by using :refer-macros as above. When using ClojureScript v0.0-2755 or above, if (:require [secretary.core :as secretary]) is used, macros will be automatically aliased to secretary, e.g. secretary/defroute.

Basic routing and dispatch

Secretary is built around two main goals: creating route matchers and dispatching actions. Route matchers match and extract parameters from URI fragments and actions are functions which accept those parameters.

defroute is Secretary's primary macro for defining a link between a route matcher and an action. The signature of this macro is [name? route destruct & body]. We will skip the name? part of the signature for now and return to it when we discuss named routes. To get clearer picture of this let's define a route for users with an id.

(defroute "/users/:id" {:as params}
  (js/console.log (str "User: " (:id params))))

In this example "/users/:id" is route, the route matcher, {:as params} is destruct, the destructured parameters extracted from the route matcher result, and the remaining (js/console.log ...) portion is body, the route action.

Before going in to more detail let's try to dispatch our route.

(secretary/dispatch! "/users/gf3")

With any luck, when we refresh the page and view the console we should see that User: gf3 has been logged somewhere.

Route matchers

By default the route matcher may either be a string or regular expression. String route matchers have special syntax which may be familiar to you if you've worked with Sinatra or Ruby on Rails. When secretary/dispatch! is called with a URI it attempts to find a route match and it's corresponding action. If the match is successful, parameters will be extracted from the URI. For string route matchers these will be contained in a map; for regular expressions a vector.

In the example above, the route matcher "/users/:id" successfully matched against "/users/gf3" and extracted {:id "gf3} as parameters. You can refer to the table below for more examples of route matchers and the parameters they return when matched successfully.

Parameter destructuring

Now that we understand what happens during dispatch we can look at the destruct argument of defroute. This part is literally sugar around let. Basically whenever one of our route matches is successful and extracts parameters this is where we destructure them. Under the hood, for example with our users route, this looks something like the following.

(let [{:as params} {:id "gf3"}]
  ...)

Given this, it should be fairly easy to see that we could have have written

(defroute "/users/:id" {id :id}
  (js/console.log (str "User: " id)))

and seen the same result. With string route matchers we can go even further and write

(defroute "/users/:id" [id]
  (js/console.log (str "User: " id)))

which is essentially the same as saying {:keys [id]}.

For regular expression route matchers we can only use vectors for destructuring since they only ever return vectors.

(defroute #"/users/(\d+)" [id]
  (js/console.log (str "User: " id)))

Query parameters

If a URI contains a query string it will automatically be extracted to :query-params for string route matchers and to the last element for regular expression matchers.

(defroute "/users/:id" [id query-params]
  (js/console.log (str "User: " id))
  (js/console.log (pr-str query-params)))

(defroute #"/users/(\d+)" [id {:keys [query-params]}]
  (js/console.log (str "User: " id))
  (js/console.log (pr-str query-params)))

;; In both instances...
(secretary/dispatch! "/users/10?action=delete")
;; ... will log
;; User: 10
;; "{:action \"delete\"}"

Named routes

While route matching and dispatch is by itself useful, it is often necessary to have functions which take a map of parameters and return a URI. By passing an optional name to defroute Secretary will define this function for you.

(defroute users-path "/users" []
  (js/console.log "Users path"))

(defroute user-path "/users/:id" [id]
  (js/console.log (str "User " id "'s path"))

(users-path) ;; => "/users"
(user-path {:id 1}) ;; => "/users/1"

This also works with :query-params.

(user-path {:id 1 :query-params {:action "delete"}})
;; => "/users/1?action=delete"

If the browser you're targeting does not support HTML5 history you can call

(secretary/set-config! :prefix "#")

to prefix generated URIs with a "#".

(user-path {:id 1})
;; => "#/users/1"

This scheme doesn't comply with URI spec

Beware that using :prefix that way will make resulting URIs no longer compliant with standard URI syntax – the fragment must be the last part of the URI after the query). Indeed, the syntax of a URI is defined as:

scheme:[//[user:password@]host[:port]][/]path[?query][#fragment]

secretary adds a # after the path so it makes the fragment hide the query. For instance, the following URL is comprehended in different ways by secretary and the spec:

https://www.example.com/path/of/app#path/inside/app?query=params&as=defined&by=secretary

• the fragment is "path/inside/app?query=params&as=defined&by=secretary" for standard libraries, but is "path/inside/app" according to Secretary

• the query is "" for standard libraries, but is "query=params&as=defined&by=secretary" according to Secretary

Available protocols

You can extend Secretary's protocols to your own data types and records if you need special functionality.

• IRenderRoute
• IRouteMatches

IRenderRoute

Most of the time the defaults will be good enough but on occasion you may need custom route rendering. To do this implement IRenderRoute for your type or record.

(defrecord User [id]
  secretary/IRenderRoute
  (render-route [_]
    (str "/users/" id))

  (render-route [this params]
    (str (secretary/render-route this) "?"
         (secretary/encode-query-params params))))

(secretary/render-route (User. 1))
;; => "/users/1"
(secretary/render-route (User. 1) {:action :delete})
;; => "/users/1?action=delete"

IRouteMatches

It is seldom you will ever need to create your own route matching implementation as the built in String and RegExp routes matchers should be fine for most applications. Still, if you have a suitable use case then this protocol is available. If your intention is to is to use it with defroute your implementation must return a map or vector.

Example with goog.History

(ns example
  (:require [secretary.core :as secretary :refer-macros [defroute]]
            [goog.events :as events])
  (:import [goog History]
           [goog.history EventType]))

(def application
  (js/document.getElementById "application"))

(defn set-html! [el content]
  (aset el "innerHTML" content))

(secretary/set-config! :prefix "#")

;; /#/
(defroute home-path "/" []
  (set-html! application "<h1>OMG! YOU'RE HOME!</h1>"))

;; /#/users
(defroute users-path "/users" []
  (set-html! application "<h1>USERS!</h1>"))

;; /#/users/:id
(defroute user-path "/users/:id" [id]
  (let [message (str "<h1>HELLO USER <small>" id "</small>!</h1>")]
    (set-html! application message)))

;; /#/777
(defroute jackpot-path "/777" []
  (set-html! application "<h1>YOU HIT THE JACKPOT!</h1>"))

;; Catch all
(defroute "*" []
  (set-html! application "<h1>LOL! YOU LOST!</h1>"))

;; Quick and dirty history configuration.
(doto (History.)
  (events/listen EventType.NAVIGATE #(secretary/dispatch! (.-token %)))
  (.setEnabled true))

Contributors

• @gf3 (Gianni Chiappetta)
• @noprompt (Joel Holdbrooks)
• @joelash (Joel Friedman)
• @james-henderson (James Henderson)
• @the-kenny (Moritz Ulrich)
• @timgilbert (Tim Gilbert)
• @bbbates (Brendan)
• @travis (Travis Vachon)

Committers

• @gf3 (Gianni Chiappetta)
• @noprompt (Joel Holdbrooks)
• @joelash (Joel Friedman)

License

Distributed under the Eclipse Public License, the same as Clojure.