Command.swift

struct FetchPlayers: Command {
    var session = URLSession.shared
    
    func execute(state: State, reactor: Reactor<State>) {
        session.dataTask(with: fetchPlayerURL) { data, response, error in
            if error {
                reactor.fire(event: DisplayError(message: "Error fetching players"))
            }
            else {
                var players: [Player] = // handle json...
                reactor.fire(event: Update(value: players))
            }
        }.resume()
    }
}

// Caller uses:
reactor.fire(command: FetchPlayers())