yadic

Lazy maps for Clojure. Useful as a dependency injection container, and for other purposes.

A rough port of yadic to Clojure, with thanks to Dan Bodart for the original idea and implementation.

Usage

Similarities to Stuart Sierra's Component

yadic is similar in some ways to Component

The main differences are:

• Construction is lazy
• Decoration is supported as a first-class concept
• We can support components with dependencies that are not defined at compile time
• AutoCloseable components are closed by default, without additional coding
• Container/system is not a persistent data structure
• Less boilerplate. i.e. no (start [this] (assoc this :some-component-key (some-component-constructor some-dependency))
• The concepts of constructor definitions (System/Component or Activators in yadic) and a container of the instances created by the Activators/Components are decomplected
• Systems/Containers can be scope- we support having a application-scoped set of dependencies, which are then used by components in an application-scoped System/Container

Finally, and most importantly, yadic is intended to be a more general library than Component. This is demonstrated by the drop-in replacement for Component, impemented with yadic and the drop-in replacement for Prismatic's excellent Graph library (see section below).

Benefits over Component

Laziness

Lazy instantiation means we can use a complete system definition without worrying about the overhead of instantiating components which we will not use.

Decoration as a first-class citizen

We find decoration to be extremely useful for separating concerns. We often build up. Compojure middleware

Container scopes

Separation of construction logic from state

Containers are not persistent data structures

Disadvantages vs. Component

Laziness

Core concepts

Activators

Container

Scopes

Decoration

Prismatic Graph drop-in

Component drop-in

License

Copyright © 2015 Matthew Savage

Distributed under the MIT license http://opensource.org/licenses/MIT