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First you have to install the Swift-WASM package from https://book.swiftwasm.org/setup.html (opens in a new tab).

You also have to install everything as described in Common tooling.

As Swift is currently a Tier 2 guest language, you can only call your whole Swift program from Golem exposed as a parameterless run function.

The easiest way to get started once the tooling is installed is to use the golem new command as described in the Quickstart.

If you prefer to do it from scratch, take the following simple Swift program saved into main.swift:

import Foundation
let date = Date()
let calendar = Calendar.current
let year = calendar.component(.year, from: date)
print("Hello world!")

And compile it to WASM using Swift-WASM:

/Library/Developer/Toolchains/swift-latest.xctoolchain/usr/bin/swiftc -target wasm32-unknown-wasi main.swift -o main.wasm -sdk /Library/Developer/Toolchains/swift-wasm-5.7.3-RELEASE.xctoolchain/usr/share/wasi-sysroot/

The resulting main.wasm is a WASM module not a component, so we have to use the tier 2 WASI adapter and wasm-tools to convert it to a WASM component

wasm-tools component new main.wasm -o component.wasm --adapt tier2/wasi_snapshot_preview1.wasm

The wasi_snapshot_preview1.wasm describes the mapping from WASI Preview1 to Preview2. You must use the version of this file packaged together with golem-cli.

Make sure you use the tier2 adapter from the golem package!

The resulting component.wasm is ready to be used with Golem.