Defining Golem Components in MoonBit

Creating a project

Golem's command line interface provides a set of predefined, Golem-specific templates to choose from as a starting point.

To get started from scratch, first create a new application using the MoonBit template:

golem app new my-app moonbit
cd my-app

An application can consist of multiple components. Add a new component by choosing from one of the available templates. To see the list of available templates, run:

golem component new

Then create a new component using the chosen template:

golem component new moonbit my-component

Specification-first approach

Golem and the MoonBit toolchain currently requires defining the component's interface using the WebAssembly Interface Type (WIT) format. See the official documentation of this format (opens in a new tab) for reference.

Each new project generated with golem contains a wit directory with at least one .wit file defining a world. This world can contain exports (exported functions and interfaces) and these exports will be the compiled Golem component's public API.

The first time a component is compiled (see the Building Components page for details), a couple of files get generated in the ffi, gen, interface and world directories. This module contains the MoonBit definitions of all the data types and interfaces defined in the WIT file(s).

To implement the specification written in WIT, the MoonBit code must implement some of these generated exported functions defined in the generated files.