Demo of using Swift in a Run Script phase in Xcode

runscript.sh

#!/bin/bash

CONFIG_PASSWORD="BE5D2905-0625-4EBF-BCA2-7F6F5D138425"
REQUIRED_CONFIG_FILE_PATH="${SRCROOT}/YourProject/App/Config/Configurations/Config-${CONFIGURATION}.plist"
CONFIG_OUTPUT_PATH="${SRCROOT}/YourProject/App/Config/Configurations/Config.json"
CONFIG_EXTENSION_OUTPUT_PATH="${SRCROOT}/YourProject/App/Config/Configurations/Config+Extension.swift"

set -e

if [ -z "${CONFIGURATION}" ]
then
    echo "CONFIGURATION environment variable is unset"
    exit 1 # Never happens
fi


if [ ! -f "${REQUIRED_CONFIG_FILE_PATH}" ]
then
    # Safety - otherwise a build may be made with the wrong config file
    echo "Missing config file ${REQUIRED_CONFIG_FILE_PATH}"
    exit 2
fi

# Use RNCryptor to encrypt the config file, seeing as we'll be using it for decryption later
swift_code() {

cat <<EOF

    import Foundation
    import RNCryptor

    // Get the contents of Config-(SCHEME).plist
    let requiredConfigParameters = NSDictionary(contentsOfFile: "$REQUIRED_CONFIG_FILE_PATH")!
    let configData = try! JSONSerialization.data(withJSONObject: requiredConfigParameters, options: [])

    // Encrypt it
    let encrypted = RNCryptor.encrypt(data: configData, withPassword: "$CONFIG_PASSWORD")
    let base64String = encrypted.base64EncodedString()

    // Base64 it and save it to a file
    try! base64String.write(toFile: "$CONFIG_OUTPUT_PATH", atomically: true, encoding: .utf8)


    // Generate an extension on Config containing the password
    let byteArray = "$CONFIG_PASSWORD".data(using: .utf8)!.map { x in return String(format:"0x%02x, ", x) }.joined()
    let configExtension = """

//! This file was generated by a RunScript Build Phase
//! ⚠️ Do not modify or commit ⚠️

extension Config {

    static func password() -> String {
        let bytes: [UInt8] = [\(byteArray)0x0] // End in 0x0 to avoid reading into random memory
        let data = Data(bytes: bytes)
        return String(data: data, encoding: .utf8)!
    }
}

"""

    try! configExtension.write(toFile: "$CONFIG_EXTENSION_OUTPUT_PATH", atomically: true, encoding: .utf8)

EOF
}

# Run the Swift code in swift_code()
echo "$(swift_code)" \
    | DEVELOPER_DIR="$DEVELOPER_DIR" \
    xcrun --sdk macosx \
    "$TOOLCHAIN_DIR/usr/bin/"swift -F "$SRCROOT/Carthage/Build/Mac/" -