peripheral.component — peripheral 0.5.4

defcomponent clj macro

(defcomponent id dependencies & component-logic)

Create new component type from a vector of dependencies (the components/fields that should be filled before the component is started, as well as a series of keyword/start/stop forms.

Each keyword has to be followed by a form that will be executed at startup and optionally a (non-keyword) function to be run at shutdown.

(defcomponent LoopRunner [f interval]
  :data   (fetch-some-data!)
  :thread (doto (Thread. #(while (not (.isInterrupted ...)) ...))
            (.start))
          #(.interrupt ^Thread %))

The results of the form/function will be assoc'd into the component. Please use the map->... function to create an instance of the record. Using fields with the namespace peripheral you can manipulate the component record directly:

(defcomponent TestComponent [...]
  :peripheral/start   #(...)      ;; called before fields are initialized
  :peripheral/started #(...)      ;; called after fields are initialized
  :peripheral/stop    #(...)      ;; called before fields are cleaned up
  :peripheral/stopped #(...))     ;; called after fields are cleaned up

Note that these take a function, not a form, and only allow for one value!

If you don't need to alter the component record, the 'on' prefix can be used to directly execute forms:

(defcomponent TestComponent [...]
  :on/start (println "starting"))

Finally, if you need access to the whole component, you can bind it to a symbol using ':this/as':

(defcomponent TestComponent [x]
  :this/as *this*
  :y (+ (:x *this*) 10)
  :z (- (:y *this*) 5))

reify-component clj macro

(reify-component & component-logic)

(reify-component dependencies & component-logic)

Create a one-off component (i.e. without creating an explicit component record). The syntax is identical to defcomponent without the class name.

(let [db-config {...}]
  (reify-component
    :db (connect! db-config) disconnect!
    ...))

The resulting value will implement all map interfaces, as well as the com.stuartsierra.component/Lifecycle protocol.

restart clj

(restart component)

Restart the given component by calling stop and start.