public override void Visit(Identifier function)
{
if (_context == null)
{
_result = L.Expression.Constant(_parameters[function.Name]);
}
else
{
var args = new ParameterArgs();
OnEvaluateParameter(function.Name, args);
if (args.HasResult)
{
_result = L.Expression.Constant(args.Result);
return;
}
_result = L.Expression.PropertyOrField(_context, function.Name);
}
}
/// <summary>
/// Parameter evaluator called off by function EvaluateExpression so as to elimiate the need of trying to cast the expression parameters to a more defined type.
/// Additionally it adds the possibility that an expression parameter itself can be of complex type.
/// </summary>
/// <param name="name">name of the parameter</param>
/// <param name="args">ParameterArgs object where to store the evaluation result</param>
private void EvaluateParam(string name, ParameterArgs args)
{
if (this._definesHandler.SubstitutionTokens.ContainsKey(name))
{
object substituionText;
this._definesHandler.SubstitutionTokens.TryGetValue(name, out substituionText);
Expression parameterExpression = new Expression((string)substituionText);
parameterExpression.EvaluateParameter += EvaluateParam;
try
{
args.Result = parameterExpression.Evaluate();
}
catch (EvaluationException)
{
//in case an exception occurred we do not set args and hence the evaluation will be undefined
}
}
//in case the key is not found we do not set args and hence the evaluation will be undefined
}
private void OnEvaluateParameter(string name, ParameterArgs args) => EvaluateParameter?.Invoke(name, args);
