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A .NET State Machine Toolkit - Part III

, 26 Oct 2006 CPOL 164.1K 907 132
Using code generation with the .NET state machine toolkit.
 * Created by: Leslie Sanford
 * Contact:
 * Last modified: 10/01/2005

using System;
using System.CodeDom;
using System.Collections;

namespace StateMachineToolkit
	/// <summary>
	/// Builds the method responsible for initializing the transitions.
	/// </summary>
    internal class TransitionInitializeBuilder
        #region TransitionInitializeBuilder Members

        #region Fields

        // The state machine's transitions.
        private IDictionary stateTransitions;

        // The built method.
        private CodeMemberMethod result = new CodeMemberMethod();


        #region Construction

        /// <summary>
        /// Initializes a new instance of the TransitionInitializeBuilder class
        /// with the specified state transition table.
        /// </summary>
        /// <param name="stateTransitions">
        /// The state transitions. 
        /// </param>
		public TransitionInitializeBuilder(IDictionary stateTransitions)
            this.stateTransitions = stateTransitions;


        #region Methods

        /// <summary>
        /// Builds the method.
        /// </summary>
        public void Build()
            result = new CodeMemberMethod();
            result.Name = "InitializeTransitions";
            result.Attributes = MemberAttributes.Private;

            CodeVariableDeclarationStatement transDeclaration = 
                new CodeVariableDeclarationStatement(typeof(Transition), "trans");


            CodeThisReferenceExpression thisReference = 
                new CodeThisReferenceExpression();
            CodeTypeReferenceExpression eventTypeReference = 
                new CodeTypeReferenceExpression("EventType");
            CodeExpression sourceStateReference;
            CodeExpression eventReference;
            CodeExpression guardReference;
            CodeExpression actionReference;
            CodeExpression targetStateReference;
            CodeObjectCreateExpression transCreate;
            CodePropertyReferenceExpression transProperty;
            CodeMethodInvokeExpression addInvoke;
            CodeVariableReferenceExpression transReference = 
                new CodeVariableReferenceExpression("trans");
            CodeAssignStatement transAssign;
            CodeCastExpression eventCast;

            TransitionRowCollection transRowCollection;

            foreach(DictionaryEntry entry in stateTransitions)
                transRowCollection = (TransitionRowCollection)entry.Value;

                foreach(TransitionRow transRow in transRowCollection)
                    sourceStateReference = new CodeFieldReferenceExpression(
                        thisReference, "state" + entry.Key.ToString());

                    eventReference = new CodeFieldReferenceExpression(
                        eventTypeReference, transRow.Event);

                    // If there is a guard for this transition.
                    if(transRow.Guard != null && transRow.Guard != string.Empty)
                        // Create a reference to the guard.
                        guardReference = new CodeFieldReferenceExpression(
                            thisReference, "guard" + transRow.Guard);
                    // Else there is no guard for this transition.
                        // Create a null reference for the guard.
                        guardReference = new CodePrimitiveExpression(null);

                    // If there is an action for this transition.
                    if(transRow.Action != null && transRow.Action != string.Empty)
                        // Create a reference to the action.
                        actionReference = new CodeFieldReferenceExpression(
                            thisReference, "action" + transRow.Action);
                    // Else there is no action for this transition.
                        // Create a null reference for the action.
                        actionReference = new CodePrimitiveExpression(null);

                    // If there is a target state for this transition.
                    if(transRow.Target != null && transRow.Target != string.Empty)
                        // Create a reference to the state target.
                        targetStateReference = new CodeFieldReferenceExpression(
                            thisReference, "state" + transRow.Target);
                    // Else there is no target state for this transition (it is an 
                    // internal transition).
                        // Create a null reference for the target state.
                        targetStateReference = new CodePrimitiveExpression(null);

                    // Create and initialize the transition and it to the collection
                    // of transitions for the specified state.

                    transCreate = new CodeObjectCreateExpression();

                    transCreate.CreateType = new CodeTypeReference(typeof(Transition));

                    transAssign = new CodeAssignStatement(transReference, transCreate);


                    eventCast = new CodeCastExpression(typeof(int), eventReference);

                    transProperty = new CodePropertyReferenceExpression(
                        sourceStateReference, "Transitions");

                    addInvoke = new CodeMethodInvokeExpression(transProperty,
                        "Add", new CodeExpression[] { eventCast, transReference });


        #region Properties

        /// <summary>
        /// Gets the built method.
        /// </summary>
        public CodeMemberMethod Result
                return result;



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This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)


About the Author

Leslie Sanford
United States United States
Aside from dabbling in BASIC on his old Atari 1040ST years ago, Leslie's programming experience didn't really begin until he discovered the Internet in the late 90s. There he found a treasure trove of information about two of his favorite interests: MIDI and sound synthesis.

After spending a good deal of time calculating formulas he found on the Internet for creating new sounds by hand, he decided that an easier way would be to program the computer to do the work for him. This led him to learn C. He discovered that beyond using programming as a tool for synthesizing sound, he loved programming in and of itself.

Eventually he taught himself C++ and C#, and along the way he immersed himself in the ideas of object oriented programming. Like many of us, he gotten bitten by the design patterns bug and a copy of GOF is never far from his hands.

Now his primary interest is in creating a complete MIDI toolkit using the C# language. He hopes to create something that will become an indispensable tool for those wanting to write MIDI applications for the .NET framework.

Besides programming, his other interests are photography and playing his Les Paul guitars.

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