ExpressionEvaluator.cs

using System.Threading.Tasks;
using Waher.Script;
using Waher.Script.Persistence.SQL;
 
namespace Waher.Persistence.FullTextSearch.PropertyEvaluators
{
    public class ExpressionEvaluator : IPropertyEvaluator
    {
        private Expression expression;
        private ObjectProperties variables;
 
        public ExpressionEvaluator()
        {
        }
 
        public Task Prepare(string Definition)
        {
            this.expression = new Expression(Definition);
            return Task.CompletedTask;
        }
 
        public Task<object> Evaluate(object Instance)
        {
            if (this.variables is null)
                this.variables = new ObjectProperties(Instance, new Variables());
            else
                this.variables.Object = Instance;
 
            return this.expression.EvaluateAsync(this.variables);
        }
    }
}