Compiling a Swift module

Before you can import the generated Swift bindings as a module (say, to use them from your application, or to try them out using swift on the command-line) you first need to compile them into a Swift module.

To do so, you'll need both the generated .swift file and the corresponding .modulemap file, which tells Swift how to expose the underlying C FFI layer. Use swiftc to combine the cdylib from your Rust crate with the generated Swift bindings:

    -module-name example                         # Name for resulting Swift module
    -emit-library -o libexample.dylib            # File to link with if using Swift REPL
    -emit-module -emit-module-path ./            # Output directory for resulting module
    -L ./target/debug/                           # Directory containing compiled Rust crate
    -lexample                                    # Name of compiled Rust crate cdylib
    -Xcc -fmodule-map-file=exampleFFI.modulemap  # The modulemap file from above
    example.swift                                # The generated bindings file

This will produce an example.swiftmodule file that can be loaded by other Swift code or used from the Swift command-line REPL.

If you are creating an XCFramework with this code, make sure to rename the modulemap file to module.modulemap, the default value expected by Clang and XCFrameworks for exposing the C FFI library to Swift.