#region Disclaimer / License
// Copyright (C) 2010, Jackie Ng
// http://trac.osgeo.org/mapguide/wiki/maestro, jumpinjackie@gmail.com
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
//
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
// Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
//
#endregion
using System;
using System.Collections.Generic;
using System.Text;
using System.Globalization;
using OSGeo.MapGuide.MaestroAPI.Exceptions;
using OSGeo.MapGuide.MaestroAPI.Feature;
namespace OSGeo.MapGuide.MaestroAPI.Expression
{
///
/// A subclass that supports expression evaluation
///
internal class ExpressionFeatureReader : ReaderBase
{
private ExpressionEngine _exprEngine;
private ReaderBase _reader;
///
/// Initializes a new instance of the class.
///
/// The reader.
public ExpressionFeatureReader(ReaderBase reader)
: this(reader, System.Threading.Thread.CurrentThread.CurrentCulture)
{
}
///
/// Initializes a new instance of the class.
///
/// The reader.
///
public ExpressionFeatureReader(ReaderBase reader, CultureInfo ci)
: base()
{
_reader = reader;
_exprEngine = new ExpressionEngine(_reader, ci);
}
///
/// Evaluates the specified expression against the current row. If evaluation
/// fails, null is returned.
///
/// The expression.
///
public object Evaluate(string expression)
{
return _exprEngine.Evaluate(expression);
}
///
/// Evaluates the specified expression returning a strongly-typed value. The specified expression
/// must evaluate to the type parameter specified (or inferred) in the call.
///
///
///
/// The evaluated result
/// Thrown if evaluation fails
public T Evaluate(string expression)
{
try
{
return _exprEngine.Evaluate(expression);
}
catch
{
throw new ExpressionException(expression);
}
}
public override Type GetFieldType(int i)
{
return _reader.GetFieldType(i);
}
public override string GetName(int index)
{
return _reader.GetName(index);
}
public override Schema.PropertyValueType GetPropertyType(int index)
{
return _reader.GetPropertyType(index);
}
public override Schema.PropertyValueType GetPropertyType(string name)
{
return _reader.GetPropertyType(name);
}
public override ReaderType ReaderType
{
get { return _reader.ReaderType; }
}
protected override IRecord ReadNextRecord()
{
if (_reader.ReadNext())
{
_exprEngine.UpdateVariables();
return _reader.Current;
}
return null;
}
}
}