Component

A component is an encapsulated block of code that can be assembled together with a base and a set of other components into services, libraries or tools. Components achieve encapsulation and composability by separating their private implementation from their public interface:

Each component lives in a separate directory under the components directory, and contains a src, test and resources directory:

▾ workspace
  ▾ components
    ▾ mycomponent
      ▸ src
      ▸ test
      ▸ resources

The src directory contains at least two namespaces, one for the interface and one for the implementation:

▾ src
    interface.clj
    core.clj

A component's interface is a namespace that exposes a collection of functions for other components or bases to call. Each function in a component’s interface “passes-through” to an equivalent function in its private implementation (the core namespace in this example). This “pass-through” approach enables full code navigation and refactoring, whilst maintaining encapsulation.

Code examples of components can be found in the RealWorld example app and in the Polylith Tool.