Delegates by Example Part 3

3/27/2017

using System;
using System.Collections.Generic;

/* This example shows one way of using delegates in a command parser
 * The final output of this example will be
 * doHello function called.
 * doWorld function called.
 * doThere function called.
 * doWorld function called.
 *
 * Notice in this example the delegate and the associated functions don't accept any parameters.
 * Delegates don't have to have parameters, infact, they can also have a return value
 */
namespace DelegatesTutorial
{
    // Declare the delegate to be used later, this sets the return type and expected parameters
    // for the delegate. All functions to be included must have the same return type and parameter list.
    delegate void myDelegate();
    // Declare a class to contain the keyword and the delegate
    class Command
    {
        public string Keyword = default(string);
        public myDelegate CmdPointer;
        public Command(string sKeyword, myDelegate dPointer)
        {
            Keyword = sKeyword;
            CmdPointer = dPointer;
        }
    }

    class Example3
    {
        // Instead of creating a list of delegates, we'll create a list of the command class
        List<Command> Commands = new List<Command>();

        public Example3()
        {
            // We'll now add three commands
            Commands.Add(new Command("hello", new myDelegate(doHello)));
            Commands.Add(new Command("there", new myDelegate(doThere)));
            Commands.Add(new Command("world", new myDelegate(doWorld)));

            // Let's use the command parser
            CommandParser("Hello");
            CommandParser("world");
            CommandParser("there");
            CommandParser("world");
        }

        // Here's the actual command parser. It simply compares text then calls the
        // appropriate function through the delegate
        void CommandParser(string CommandToParse)
        {
            foreach (Command c in Commands)
            {
                if (c.Keyword.ToLower() == CommandToParse.ToLower())
                c.CmdPointer();
            }
        }

        // These are the functions to be called by the delegate
        void doHello()
        {
            Console.WriteLine("doHello function called.");
        }
        void doThere()
        {
            Console.WriteLine("doThere function called.");
        }
        void doWorld()
        {
            Console.WriteLine("doWorld function called.");
        }
    }
}

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