https://github.com/camsaul/external-fn

Small Clojure lib to define functions whose implementations will be provided elsewhere
https://github.com/camsaul/external-fn

clojure dependency-injection external external-fn

Last synced: 4 months ago
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Small Clojure lib to define functions whose implementations will be provided elsewhere

• Host: GitHub
• URL: https://github.com/camsaul/external-fn
• Owner: camsaul
• License: epl-2.0
• Created: 2019-06-15T04:09:25.000Z (over 5 years ago)
• Default Branch: master
• Last Pushed: 2019-06-15T05:37:44.000Z (over 5 years ago)
• Last Synced: 2024-06-02T22:46:58.115Z (9 months ago)
• Topics: clojure, dependency-injection, external, external-fn
• Language: Clojure
• Size: 15.6 KB
• Stars: 4
• Watchers: 2
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE
  • Codeowners: .github/CODEOWNERS

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A small Clojure utility library for defining abstract functions whose implementation will be provided elsewhere

(perhaps externally). Useful for dependency injection and otherwise nicely

decoupling different modules of your project from one another.

This library provides a function, `external-fn`, that you can use to create an externally-defined function.

This resulting object works exactly like a normal Clojure function, but will throw an Exception if invoked before

an instance has been provided:

```clj

(require '[external-function.core :as external-fn])

(def f (external-fn/external-fn))

(f) ;-> AbstractMethodError

```

You can provide an implementation with `provide-impl!`:

```clj

;; provide an implementation

(external-fn/provide-impl! f (constantly :ok))

;; now function will work as expected

(f) ;-> :ok

```

This library also provides a `defexternal` macro to define an external function with almost the exact same syntax as `defn`; the usual

nice-to-have metadata like `:arglists` is provided as well.

```clj

(external-fn/defexternal my-fn

  "You can add docstrings"

  {:can-add-attribute-maps? true}

  [x])

(external-fn/provide-impl! my-fn (fn [x] (+ x x)))

(my-fn 2) ;-> 4

```