Components are the main building blocks in Polylith.

A component is an encapsulated block of code that can be assembled together with a base (it's often just a single base) and a set of components and libraries 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 often contains at least two namespaces, one for the interface and one for the implementation:

▾ src

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. You are allowed to put the implementation directly in the interface, but most of the time you want to separate the two.

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

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