Visitor pattern partial implementation

Attempted to implement visitor pattern but I'm coming up on more barriers than it solves. Restoring from DTOs is fine and requires the pattern to be implemented on the DTOs. To create from IParameter, these would also need another implementation of the visitor pattern which tightly couples the concrete implementation of what criteria exist into the core library which is unacceptable. A more suitable pattern is required.
stuarta0 · May 14, 2015 · 1090f72 · 1090f72
1 parent 17e5a01
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Showing 15 changed files with 199 additions and 51 deletions.
diff --git a/lib/Standalone/Serialization/Assemblers/Criterion/CreateVisitor.cs b/lib/Standalone/Serialization/Assemblers/Criterion/CreateVisitor.cs
@@ -0,0 +1,48 @@
+using dbqf.Criterion;
+using Standalone.Serialization.DTO.Criterion;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Standalone.Serialization.Assemblers.Criterion
+{
+    public class CreateVisitor : IParameterDTOVisitor
+    {
+        /// <summary>
+        /// Gets the ParameterDTO constructed after visiting the equivalent IParameter.
+        /// </summary>
+        public ParameterDTO Parameter { get; private set; }
+
+        public void Visit(DTO.Criterion.SimpleParameterDTO dto)
+        {
+            throw new NotImplementedException();
+        }
+
+        public void Visit(DTO.Criterion.LikeParameterDTO dto)
+        {
+            throw new NotImplementedException();
+        }
+
+        public void Visit(DTO.Criterion.ConjunctionDTO dto)
+        {
+            throw new NotImplementedException();
+        }
+
+        public void Visit(DTO.Criterion.NotParameterDTO dto)
+        {
+            throw new NotImplementedException();
+        }
+
+        public void Visit(DTO.Criterion.NullParameterDTO dto)
+        {
+            throw new NotImplementedException();
+        }
+
+        public void Visit(DTO.Criterion.BetweenParameterDTO dto)
+        {
+            throw new NotImplementedException();
+        }
+    }
+}
diff --git a/lib/Standalone/Serialization/Assemblers/Criterion/IParameterDTO.cs b/lib/Standalone/Serialization/Assemblers/Criterion/IParameterDTO.cs
@@ -0,0 +1,13 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Standalone.Serialization.Assemblers.Criterion
+{
+    public interface IParameterDTO
+    {
+        void Accept(IParameterDTOVisitor visitor);
+    }
+}
diff --git a/lib/Standalone/Serialization/Assemblers/Criterion/IParameterDTOVisitor.cs b/lib/Standalone/Serialization/Assemblers/Criterion/IParameterDTOVisitor.cs
@@ -0,0 +1,19 @@
+using Standalone.Serialization.DTO.Criterion;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Standalone.Serialization.Assemblers.Criterion
+{
+    public interface IParameterDTOVisitor
+    {
+        void Visit(SimpleParameterDTO dto);
+        void Visit(LikeParameterDTO dto);
+        void Visit(ConjunctionDTO dto);
+        void Visit(NotParameterDTO dto);
+        void Visit(NullParameterDTO dto);
+        void Visit(BetweenParameterDTO dto);
+    }
+}
diff --git a/lib/Standalone/Serialization/Assemblers/Criterion/ParameterAssembler.cs b/lib/Standalone/Serialization/Assemblers/Criterion/ParameterAssembler.cs
@@ -10,49 +10,17 @@ namespace Standalone.Serialization.Assemblers.Criterion
 {
     public class ParameterAssembler : IAssembler<IParameter, ParameterDTO>
     {
-        /*
-         * Maybe we can use the visitor pattern on ParameterDTO to give type-safe Create/Restore here?
-         * e.g.
-         *  interface IParameterDTOVisitor
-         *  {
-         *      Visit(SimpleParameterDTO);
-         *      Visit(LikeParameterDTO);
-         *      Visit(ConjunctionDTO);
-         *      etc...
-         *  }
-         *  interface IParameterDTO
-         *  {
-         *      Accept(IParameterDTOVisitor);
-         *  }
-         *  ParameterDTO.Accept(IParameterDTOVisitor pv)
-         *  {
-         *      pv.Visit(this);
-         *  }
-         *  
-         *  ParameterDTO : IParameterDTO
-         *  ParameterAssembler : IParameterDTOVisitor
-         *  
-         *  ParameterAssembler._restored;
-         *  ParameterAssembler.Restore(ParameterDTO dto)
-         *  {
-         *      dto.Accept(this);
-         *      return _restored;
-         *  }
-         *  ParameterAssembler.Visit(ConjunctionDTO dto)
-         *  {
-         *      var c = new Conjunction();
-         *      foreach (var inner in dto.Parameters)
-         *      {
-         *          inner.Accept(this);
-         *          c.Add(_restored);
-         *      }
-         *      _restored = c;
-         *  }
-         */
+        private FieldPathAssembler _pathAssembler;
+        public ParameterAssembler(FieldPathAssembler pathAssembler)
+        {
+            _pathAssembler = pathAssembler;
+        }
 
         public IParameter Restore(ParameterDTO dto)
         {
-            throw new NotImplementedException();
+            var restorer = new RestoreVisitor(_pathAssembler);
+            dto.Accept(restorer);
+            return restorer.Parameter;
         }
 
         public ParameterDTO Create(IParameter source)

diff --git a/lib/Standalone/Serialization/Assemblers/Criterion/RestoreVisitor.cs b/lib/Standalone/Serialization/Assemblers/Criterion/RestoreVisitor.cs
@@ -0,0 +1,63 @@
+using dbqf.Criterion;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Standalone.Serialization.Assemblers.Criterion
+{
+    public class RestoreVisitor : IParameterDTOVisitor
+    {
+        private FieldPathAssembler _pathAssembler;
+        public RestoreVisitor(FieldPathAssembler pathAssembler)
+        {
+            _pathAssembler = pathAssembler;
+        }
+
+        /// <summary>
+        /// Gets the Parameter constructed after visiting the equivalent ParameterDTO.
+        /// </summary>
+        public IParameter Parameter { get; private set; }
+
+        public void Visit(DTO.Criterion.SimpleParameterDTO dto)
+        {
+            Parameter = new SimpleParameter(_pathAssembler.Restore(dto.Path), dto.Operator, dto.Value);
+        }
+
+        public void Visit(DTO.Criterion.LikeParameterDTO dto)
+        {
+            // TODO
+            Parameter = new LikeParameter(_pathAssembler.Restore(dto.Path), null);
+        }
+
+        public void Visit(DTO.Criterion.ConjunctionDTO dto)
+        {
+            var restorer = new RestoreVisitor(_pathAssembler);
+            var con = new Conjunction();
+            foreach (var dto2 in dto.Parameters)
+            {
+                dto2.Accept(restorer);
+                con.Add(restorer.Parameter);
+            }
+            Parameter = con;
+        }
+
+        public void Visit(DTO.Criterion.NotParameterDTO dto)
+        {
+            var restorer = new RestoreVisitor(_pathAssembler);
+            dto.Parameter.Accept(restorer);
+            Parameter = new NotParameter(restorer.Parameter);
+        }
+
+        public void Visit(DTO.Criterion.NullParameterDTO dto)
+        {
+            Parameter = new NullParameter(_pathAssembler.Restore(dto.Path));
+        }
+
+        public void Visit(DTO.Criterion.BetweenParameterDTO dto)
+        {
+            Parameter = new BetweenParameter(_pathAssembler.Restore(dto.Path), dto.Low, dto.High);
+        }
+    }
+}
diff --git a/lib/Standalone/Serialization/DTO/Criterion/BetweenParameterDTO.cs b/lib/Standalone/Serialization/DTO/Criterion/BetweenParameterDTO.cs
@@ -26,5 +26,10 @@ public class BetweenParameterDTO : ParameterDTO
         [XmlElement]
         public object Low { get; set; }
         public bool ShouldSerializeLow() { return Low != null; }
+
+        public override void Accept(Assemblers.Criterion.IParameterDTOVisitor visitor)
+        {
+            visitor.Visit(this);
+        }
     }
 }
diff --git a/lib/Standalone/Serialization/DTO/Criterion/ConjunctionDTO.cs b/lib/Standalone/Serialization/DTO/Criterion/ConjunctionDTO.cs
@@ -14,5 +14,10 @@ public class ConjunctionDTO : ParameterDTO
     {
         [XmlText]
         public IList<ParameterDTO> Parameters { get; set; }
+
+        public override void Accept(Assemblers.Criterion.IParameterDTOVisitor visitor)
+        {
+            visitor.Visit(this);
+        }
     }
 }
diff --git a/lib/Standalone/Serialization/DTO/Criterion/LikeParameterDTO.cs b/lib/Standalone/Serialization/DTO/Criterion/LikeParameterDTO.cs
@@ -13,6 +13,9 @@ public class LikeParameterDTO : ParameterDTO
         [XmlElement]
         public FieldPathDTO Path { get; set; }
 
-
+        public override void Accept(Assemblers.Criterion.IParameterDTOVisitor visitor)
+        {
+            visitor.Visit(this);
+        }
     }
 }
diff --git a/lib/Standalone/Serialization/DTO/Criterion/NotParameterDTO.cs b/lib/Standalone/Serialization/DTO/Criterion/NotParameterDTO.cs
@@ -1,4 +1,5 @@
-using System;
+using dbqf.Criterion;
+using System;
 using System.Collections.Generic;
 using System.ComponentModel;
 using System.Linq;
@@ -16,5 +17,10 @@ public class NotParameterDTO : ParameterDTO
         /// </summary>
         [XmlText]
         public ParameterDTO Parameter { get; set; }
+
+        public override void Accept(Assemblers.Criterion.IParameterDTOVisitor visitor)
+        {
+            visitor.Visit(this);
+        }
     }
 }
diff --git a/lib/Standalone/Serialization/DTO/Criterion/NullParameterDTO.cs b/lib/Standalone/Serialization/DTO/Criterion/NullParameterDTO.cs
@@ -1,4 +1,5 @@
-using System;
+using dbqf.Criterion;
+using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
@@ -12,5 +13,10 @@ public class NullParameterDTO : ParameterDTO
     {
         [XmlElement]
         public FieldPathDTO Path { get; set; }
+
+        public override void Accept(Assemblers.Criterion.IParameterDTOVisitor visitor)
+        {
+            visitor.Visit(this);
+        }
     }
 }
diff --git a/lib/Standalone/Serialization/DTO/Criterion/ParameterDTO.cs b/lib/Standalone/Serialization/DTO/Criterion/ParameterDTO.cs
@@ -7,11 +7,13 @@
 using ProtoBuf;
 using System.Xml.Serialization;
 using System.ComponentModel;
+using Standalone.Serialization.Assemblers.Criterion;
 
 namespace Standalone.Serialization.DTO.Criterion
 {
     [XmlRoot("Parameter")]
-    public class ParameterDTO
+    public abstract class ParameterDTO : IParameterDTO
     {
+        public abstract void Accept(IParameterDTOVisitor visitor);
     }
 }
diff --git a/lib/Standalone/Serialization/DTO/Criterion/SimpleParameterDTO.cs b/lib/Standalone/Serialization/DTO/Criterion/SimpleParameterDTO.cs
@@ -26,5 +26,10 @@ public class SimpleParameterDTO : ParameterDTO
         [XmlElement]
         public object Value { get; set; }
         public bool ShouldSerializeValue() { return Value != null; }
+
+        public override void Accept(Assemblers.Criterion.IParameterDTOVisitor visitor)
+        {
+            visitor.Visit(this);
+        }
     }
 }
diff --git a/lib/Standalone/Standalone.csproj b/lib/Standalone/Standalone.csproj
@@ -116,7 +116,11 @@
     <Compile Include="Program.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />
     <Compile Include="Serialization\Assemblers\ConfigurationAssembler.cs" />
+    <Compile Include="Serialization\Assemblers\Criterion\IParameterDTO.cs" />
+    <Compile Include="Serialization\Assemblers\Criterion\IParameterDTOVisitor.cs" />
     <Compile Include="Serialization\Assemblers\Criterion\ParameterAssembler.cs" />
+    <Compile Include="Serialization\Assemblers\Criterion\CreateVisitor.cs" />
+    <Compile Include="Serialization\Assemblers\Criterion\RestoreVisitor.cs" />
     <Compile Include="Serialization\Assemblers\ParserAssembler.cs" />
     <Compile Include="Serialization\Assemblers\ProjectAssembler.cs" />
     <Compile Include="Serialization\Assemblers\FieldAssembler.cs" />

diff --git a/lib/dbqf.core/Criterion/NotParameter.cs b/lib/dbqf.core/Criterion/NotParameter.cs
@@ -10,17 +10,18 @@ namespace dbqf.Criterion
     [DebuggerDisplay("NOT ({_other})")]
     public class NotParameter : IParameter
     {
-        IParameter _other;
-        public NotParameter(IParameter other)
+        public IParameter Parameter { get; private set; }
+
+        public NotParameter(IParameter p)
         {
-            _other = other;
+            Parameter = p;
         }
 
         public SqlString ToSqlString()
         {
             return new SqlString()
                 .Add("NOT (")
-                .Add(_other.ToSqlString())
+                .Add(Parameter.ToSqlString())
                 .Add(")");
         }
     }

diff --git a/lib/dbqf.core/Criterion/NullParameter.cs b/lib/dbqf.core/Criterion/NullParameter.cs
@@ -8,7 +8,7 @@ namespace dbqf.Criterion
 {
     public class NullParameter : IParameter
     {
-        private FieldPath _path;
+        public FieldPath Path { get; private set; }
 
         public NullParameter(IField field)
             : this(FieldPath.FromDefault(field))
@@ -17,13 +17,13 @@ public NullParameter(IField field)
 
         public NullParameter(FieldPath path)
         {
-            _path = path;
+            Path = path;
         }
 
         public SqlString ToSqlString()
         {
             return new SqlString()
-                .AddField(_path)
+                .AddField(Path)
                 .Add(" IS NULL");
         }
     }