darkleaf.di.core — org.clojars.darkleaf/di 2.4.0

add-side-dependency clj

(add-side-dependency dep-key)

A registry middleware for adding side dependencies. Use it for migrations or other side effects.

(defn flyway [{url "DATABASE_URL"}]
  (.. (Flyway/configure)
      ...))

(di/start ::root (di/add-side-dependency `flyway))

combine-dependencies clj

(combine-dependencies)

(combine-dependencies a b)

Combines dependencies. Use it with reduce. Dependencies are a hash map of a key and a dependency type.

env-parsing clj

(env-parsing & {:as cmap})

A registry middleware for parsing environment variables. You can define a dependency of env as a string key like "PORT", and its value will be a string. With this middleware, you can define it as a qualified keyword like :env.long/PORT, and its value will be a number. cmap is a map of prefixes and parsers.

(defn root [{port :env.long/PORT}]
  ...)

(di/start `root (di/env-parsing :env.long parse-long
                                :env.edn  edn/read-string
                                :env.json json/read-value))

fmap clj

(fmap factory f & args)

Applies f to an object that the factory produces. f accepts a built object and returns updated one.

f should not return a non-trivial instance of p/Stoppable.

(def port (-> (di/ref "PORT")
              (di/fmap parse-long)))

See ref, template.

instrument clj

(instrument f & args)

A registry middleware for instrumenting or decorating built objects. Use it for logging, schema checking, AOP, etc.

f and args are keys. Also f can be a function in term of ifn?.

A resolved f must be a function of [object key & args] -> new-object. f should not return a non-trivial instance of p/Stoppable.

It is smart enough not to instrument f's dependencies with the same f to avoid circular dependencies.

(defn stateful-instrumentaion [{state :some/state} key object arg1 arg2] ...)
(di/start ::root (di/instrument `stateful-instrumentation `arg1 ::arg2 "arg3")))

(defn stateless-instrumentaion [key object arg1 arg2 arg3] ...)
(di/start ::root (di/instrument   stateless-instrumentation `arg1 ::arg2 "arg3"))
(di/start ::root (di/instrument #'stateless-instrumentation `arg1 ::arg2 "arg3"))

See start, update-key, fmap.

opt-ref clj

(opt-ref key)

Returns a factory referencing to a possible undefined key. Produces nil in that case.

See template, ref, fmap.

ref clj

(ref key)

Returns a factory referencing to a key.

(def port (di/ref "PORT"))
(defn server [{port `port}] ...)

(def routes (di/template [["/posts" (di/ref `handler)]]))

(di/start `root {::my-abstraction (di/ref `my-implementation)})

See template, opt-ref, fmap, p/build.

start clj

(start key & middlewares)

Starts a system of dependent objects.

key is a name of the system root. Use symbols for var names, keywords for abstract dependencies, and strings for environments variables.

key is looked up in a registry. By default registry uses Clojure namespaces and system env to resolve symbols and strings, respectively.

You can extend it with registry middlewares. Each middleware can be one of the following form:

• a function registry -> key -> Factory
• a map of key and p/Factory instance
• nil, as no-op middleware
• a sequence of the previous forms

Middlewares also allows you to instrument built objects. It's useful for logging, schema validation, AOP, etc. See instrument, update-key.

(di/start `root
          {:my-abstraction implemntation
           `some-key replacement
           "LOG_LEVEL" "info"}
          [dev-middlwares test-middlewares]
          (if dev-routes?
            (di/update-key `route-data conj `dev-route-data)
          (di/instrument `log))

Returns a container contains started root of the system. The container implements AutoCloseable, Stoppable, IDeref, IFn and Indexed.

Use with-open in tests to stop the system reliably.

You can pass a vector as the key argument to start many keys:

(with-open [root (di/start [`handler `helper])]
  (let [[handler helper] root]
     ...))

See the tests for use cases. See instrument, update-key.

stop clj

(stop root)

Stops the root of a system

template clj

(template form)

Returns a factory for templating a data-structure. Replaces ref or opt-ref instances with built objects.

(def routes (di/template [["/posts" (di/ref `handler)]]))

See ref and opt-ref.

update-key clj

(update-key target f & args)

A registry middleware for updating built objects.

target is a key to update. f and args are keys. Also f can be a function in term of ifn?. f should not return a non-trivial instance of p/Stoppable.

(def routes [])
(def subsystem-routes (di/template [["/posts" (di/ref `handler)]]))

(di/start ::root (di/update-key `routes conj `subsystem-routes))

If you don't want to resolve keys like :some-name, you should use them in a in-place fn:

(di/update-key `key #(assoc %1 :some-name %2) `some-value)

See update, start, instrument, fmap.