Greetings (Delegate version)

This is the first "Hello, world" example program. This class runs a simple simulation that prints a greeting message to standard output (e.g. the console). In this example, none of the React.NET classes are subclassed to implement the simulation. The process steps are provided via a delegate, SayHello.

This example program demonstrates how a simple simulation can be created without extending any of the React.NET classes. Most simulations will probably contain subclasses of the Process class and possibly of the Simulation class.

The complete code for this example is shown below and is also available as greetings1.cs in the examples\greetings directory.

using System;
using System.Collections.Generic;
using React;

public class Greetings
{
    private Greetings() { }

    private IEnumerator<Task> SayHello(Process process, object data)
    {
        Console.WriteLine("Greetings1 says, Hello there ...");
        yield break;
    }

    public static void Main(string [] args)
    {
        Simulation sim = new Simulation();
        Greetings greetings = new Greetings();
        Process process = new Process(sim, greetings.SayHello);
        sim.Run(process);
    }
}

The Explanation

Start by including references to some of the required namespaces. The System.Collections.Generic namespace is required for the IEnumerator<Task> class. The React namespace is required for the Simulation, Task, and Process classes.

using System;
using System.Collections.Generic;
using React;

The Greetings class is derived from System.Object and contains a private constructor to prevent other classes from instantiating it.

public class Greetings
{
    private Greetings() { }

          .
          .
          .
}

The private SayHello method defines the functionality of the Process that will be created in the Main method. SayHello is the delegate used by the Process to yield its Tasks. Of course, in this case, all the Process will do is print a message and exit -- no Tasks are returned by SayHello.

The yield break; statement must be included or SayHello will not be a valid .NET iterator.

private IEnumerator<Task> SayHello(Process process, object data)
{
    Console.WriteLine("Greetings1 says, Hello there ...");
    yield break;
}

Finally, the Main method instantiates a Simulation object and a Greetings object. A new Process is created passing the constructor the SayHello delegate. The new process is passed to the Run method of the Simulation class to serve as the generator task which is executed by the Simulation, sim. When the generator task is executed, the SayHello method will get called and the greetings message printed to the console.

Simulation sim = new Simulation();
Greetings greetings = new Greetings();
Process process = new Process(sim, greetings.SayHello);
sim.Run(process);