Utilizing Keychain Services with Swift 5.9

Hello,

I'm near-brand new to writing in Swift and am attempting to write a simple VPN configuration to start an existing VPN in-app for a mobile app I'm developing for the company I work for. We're writing this in Swift in hopes of converting them to C# eventually for the mobile app's end product.

So I'm attempting to set VPN configurations using a NEVPNProtocolIKEv2() type, and when it comes to setting the server address, remote identifier, and username, it seems pretty straightforward.

However, when I try to set a password reference, I'm failing to figure out how to do so in a straight forward way. I've tried several methods from the docs and continuously yield no results, so I wanted to ask if I was doing something wrong in the following code (most of which is commented out, but indicated by single line comments where the attempts were).

/** @class VPN contains all of the configuration and handling for enacting a VPN connection */
class VPN {
    // Initialize `manager` variable with `NEVPNManager` object using @method `shared()`
    let manager = NEVPNManager.shared()
    /** @variable vpnLoadHandler handles loading the VPN and error catching? */
    private var vpnLoadHandler:
    (Error?) -> Void {
        return {
            (error:Error?) in
            if ((error) != nil) {
                print("Load VPN Configurations failed...")
                return;
            }
            // Initialize and assign `p` as `NEVPNProtocolIKEv2()` interface
            let p = NEVPNProtocolIKEv2()
            // Assign property values for the IKEv2 VPN
            p.serverAddress = "0.0.0.0"
            p.remoteIdentifier = "abc"
            p.username = "iosUser"
            // Assign string `pass` with string value of intended password
            let pass = "password"
            // Assign string `key` with string value of intended key
            let key = "pwd"
            // Create an add query to encode password as `Data` instance
            var query: [String: Any] = [kSecClass as String: kSecClassGenericPassword,
                                        kSecAttrGeneric as String: key,
                                        kSecValueData as String: pass]
            // Add the item to `passKeyValue` using `SecAddItem`
            let passKeyValue = SecItemAdd(query as CFDictionary, nil)
                // ALTERNATIVE VALUE ASSIGNMENT
            // let passKeyValue = SecItemCopyMatching(query as CFDictionary, nil)
            // Initiate search to access password from query
                // ATTEMPT 1
            /*
             var item: CFTypeRef?
             guard let existingItem = item as? [String: Any],
             let passwordData = existingItem[kSecValueData as String] as? Data,
             let password = passwordData
             else {
             print("Keychain failed...")
             }
             */
                // ATTEMPT 2
            /*
             var error: Unmanaged<CFError>?
             guard let data = SecKeyCopyExternalRepresentation(passKeyValue, &error) as Data else {
             throw error!.takeRetainedValue() as Error
             }
             */
                // ATTEMPT 3
            /*
            var error: Unmanaged<CFError>?
            guard let pkData = SecKeyCreateWithData(data as CFData,
                                                    query as CFDictionary,
                                                    &error) else {
                throw error!.takeRetainedValue() as Error
            }
             */
        }
    }
}

I'm just a little lost because as of a year ago, other similar code that I've referenced uses conventions of:

let kcs = KeychainService();
            kcs.save(key: "SHARED", value: "MY_SHARED_KEY")
            kcs.save(key: "VPN_PASSWORD", value: "MY_PASSWORD"

Why has it changed? How would I go about achieving the same thing?