PetaJson/TestCases/TestAbstractTypes.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using PetaJson;
using PetaTest;
using System.IO;

namespace TestCases
{
    abstract class Shape : IJsonWriting
    {
        [Json] public string Color;

        // Override OnJsonWriting to write out the derived class type
        void IJsonWriting.OnJsonWriting(IJsonWriter w)
        {
            w.WriteKey("kind");
            w.WriteStringLiteral(GetType().Name);
        }
    }

    class Rectangle : Shape
    {
        [Json]
        public float CornerRadius;
    }

    class Ellipse : Shape
    {
        [Json]
        public bool Filled;
    }

    [TestFixture]
    class TestAbstractTypes
    {
        static TestAbstractTypes()
        {
            // Register a type factory that can instantiate Shape objects
            Json.RegisterTypeFactory(typeof(Shape), (reader, key) =>
            {
                // This method will be called back for each key in the json dictionary
                // until an object instance is returned

                // We saved the object type in a key called "kind", look for it
                if (key != "kind")
                    return null;

                // Read the next literal (which better be a string) and instantiate the object
                return reader.ReadLiteral(literal =>
                {
                    switch ((string)literal)
                    {
                        case "Rectangle": return new Rectangle();
                        case "Ellipse": return new Ellipse();
                        default:
                            throw new InvalidDataException(string.Format("Unknown shape kind: '{0}'", literal));
                    }
                });
            });
        }

        [Test]
        public void Test()
        {
            // Create a list of shapes
            var shapes = new List<Shape>();
            shapes.Add(new Rectangle() { Color = "Red", CornerRadius = 10 });
            shapes.Add(new Ellipse() { Color="Blue", Filled = true });

            // Save it
            var json = Json.Format(shapes);

            Console.WriteLine(json);

            // Check the object kinds were written out
            Assert.Contains(json, "\"kind\": \"Rectangle\"");
            Assert.Contains(json, "\"kind\": \"Ellipse\"");

            // Reload the list
            var shapes2 = Json.Parse<List<Shape>>(json);

            // Check stuff...
            Assert.AreEqual(shapes2.Count, 2);
            Assert.IsInstanceOf<Rectangle>(shapes2[0]);
            Assert.IsInstanceOf<Ellipse>(shapes2[1]);

            Assert.AreEqual(((Rectangle)shapes2[0]).Color, "Red");
            Assert.AreEqual(((Rectangle)shapes2[0]).CornerRadius, 10);
            Assert.AreEqual(((Ellipse)shapes2[1]).Color, "Blue");
            Assert.AreEqual(((Ellipse)shapes2[1]).Filled, true);

        }
    }
}