¿Cómo combinar condiciones dinámicamente?
Esta pregunta es una mejora de la pregunta ya contestada¿Cómo aplicar múltiples condiciones de filtro (simultáneamente) en una lista?
En la pregunta arriba mencionada tenemos un método que aplicaAND
Operador en todas las especificaciones. Esto se logra utilizando LINQAll
Operador en las especificaciones.
public static List<Product> GetProductsUisngAndFilters(List<Product> productList, List<Specification<Product>> productSpecifications)
{
return productList.Where(p => productSpecifications.All(ps => ps.IsSatisfiedBy(p))).ToList();
}
Necesitamos crear un nuevo método (GetProductsUisngDynamicFilters) que sea capaz de realizarAND
, OR
yNOT
Especificaciones (y una mezcla de eso). ¿Alguna idea de cómo podemos resolver esto?
Métodos de filtro
public static class ProductFilterHelper
{
public static List<Product> GetProductsUisngAndFilters(List<Product> productList, List<Specification<Product>> productSpecifications)
{
return productList.Where(p => productSpecifications.All(ps => ps.IsSatisfiedBy(p))).ToList();
}
}
Cliente
class Program
{
static void Main(string[] args)
{
List<Product> list = new List<Product>();
Product p1 = new Product(false, 99);
Product p2 = new Product(true, 99);
Product p3 = new Product(true, 101);
Product p4 = new Product(true, 110);
Product p5 = new Product(false, 110);
list.Add(p1);
list.Add(p2);
list.Add(p3);
list.Add(p4);
list.Add(p5);
double priceLimit = 100;
List<Specification<Product>> specifications = new List<Specification<Product>>();
specifications.Add(new OnSaleSpecificationForProduct());
specifications.Add(new PriceGreaterThanSpecificationForProduct(priceLimit));
specifications.Add(new PriceGreaterThan105());
List<Product> selectedList = ProductFilterHelper.GetProductsBasedOnInputFilters(list, specifications);
Console.ReadKey();
}
}
Especificaciones abstractas
public abstract class Specification<T>
{
public abstract bool IsSatisfiedBy(T obj);
public AndSpecification<T> And(Specification<T> specification)
{
return new AndSpecification<T>(this, specification);
}
public OrSpecification<T> Or(Specification<T> specification)
{
return new OrSpecification<T>(this, specification);
}
public NotSpecification<T> Not(Specification<T> specification)
{
return new NotSpecification<T>(this, specification);
}
}
public abstract class CompositeSpecification<T> : Specification<T>
{
protected readonly Specification<T> _leftSide;
protected readonly Specification<T> _rightSide;
public CompositeSpecification(Specification<T> leftSide, Specification<T> rightSide)
{
_leftSide = leftSide;
_rightSide = rightSide;
}
}
Especificaciones genéricas
public class AndSpecification<T> : CompositeSpecification<T>
{
public AndSpecification(Specification<T> leftSide, Specification<T> rightSide)
: base(leftSide, rightSide)
{
}
public override bool IsSatisfiedBy(T obj)
{
return _leftSide.IsSatisfiedBy(obj) && _rightSide.IsSatisfiedBy(obj);
}
}
public class OrSpecification<T> : CompositeSpecification<T>
{
public OrSpecification(Specification<T> leftSide, Specification<T> rightSide)
: base(leftSide, rightSide)
{
}
public override bool IsSatisfiedBy(T obj)
{
return _leftSide.IsSatisfiedBy(obj) || _rightSide.IsSatisfiedBy(obj);
}
}
public class NotSpecification<T> : CompositeSpecification<T>
{
public NotSpecification(Specification<T> leftSide, Specification<T> rightSide)
: base(leftSide, rightSide)
{
}
public override bool IsSatisfiedBy(T obj)
{
return _leftSide.IsSatisfiedBy(obj) && !_rightSide.IsSatisfiedBy(obj);
}
}
Especificaciones del producto
public class OnSaleSpecificationForProduct : Specification<Product>
{
public override bool IsSatisfiedBy(Product product)
{
return product.IsOnSale;
}
}
public class PriceGreaterThanSpecificationForProduct : Specification<Product>
{
private readonly double _price;
public PriceGreaterThanSpecificationForProduct(double price)
{
_price = price;
}
public override bool IsSatisfiedBy(Product product)
{
return product.Price > _price;
}
}
public class PriceGreaterThan105 : Specification<Product>
{
public override bool IsSatisfiedBy(Product product)
{
return product.Price > 105;
}
}
Entidad
public class Product
{
private bool _isOnSale;
private double _price = 0.0;
public Product(bool isOnSale)
: this(isOnSale, 0.0)
{
_isOnSale = isOnSale;
}
public Product(double price)
: this(false, price)
{
_price = price;
}
public Product(bool isOnSale, double price)
{
_price = price;
_isOnSale = isOnSale;
}
public bool IsOnSale
{
get { return _isOnSale; }
}
public double Price
{
get { return _price; }
}
}