/src/NUnit/framework/Constraints/EmptyConstraint.cs

// ****************************************************************

// Copyright 2007, Charlie Poole

// This is free software licensed under the NUnit license. You may

// obtain a copy of the license at http://nunit.org

// ****************************************************************



using System;

using System.Collections;



namespace NUnit.Framework.Constraints

{

	/// <summary>

	/// EmptyConstraint tests a whether a string or collection is empty,

	/// postponing the decision about which test is applied until the

	/// type of the actual argument is known.

	/// </summary>

	public class EmptyConstraint : Constraint

	{

		private Constraint RealConstraint

		{

			get 

			{

                if (actual is string)

                    return new EmptyStringConstraint();

                else if (actual is System.IO.DirectoryInfo)

                    return new EmptyDirectoryContraint();

                else

					return new EmptyCollectionConstraint();

			}

		}

		

		/// <summary>

        /// Test whether the constraint is satisfied by a given value

        /// </summary>

        /// <param name="actual">The value to be tested</param>

        /// <returns>True for success, false for failure</returns>

		public override bool Matches(object actual)

		{

			this.actual = actual;



			return this.RealConstraint.Matches( actual );

		}



        /// <summary>

        /// Write the constraint description to a MessageWriter

        /// </summary>

        /// <param name="writer">The writer on which the description is displayed</param>

		public override void WriteDescriptionTo(MessageWriter writer)

		{

			this.RealConstraint.WriteDescriptionTo( writer );

		}

	}

}