static void Main(string[] args)
{
var apple = new Product("Apple", Color.Green, Size.Small);
var tree = new Product("Tree", Color.Green, Size.Large);
var house = new Product("House", Color.Blue, Size.Large);
Product[] products = { apple, tree, house };
var pf = new ProductFilter();
Console.WriteLine("Green products (old): ");
foreach (var p in pf.FilterByColor(products, Color.Green))
{
Console.WriteLine($" - {p.Name} is green");
}
var bf = new BetterFilter();
Console.WriteLine("Green products (new): ");
foreach (var p in bf.Filter(products, new ColorSpecification(Color.Green)))
{
Console.WriteLine($" - {p.Name} is green");
}
Console.WriteLine("Large blue items:");
foreach (var p in bf.Filter(products,
new AndSpecification <Product>(new ColorSpecification(Color.Blue)
, new SizeSpecification(Size.Large))))
{
Console.WriteLine($" - {p.Name} is big and blue");
}
Console.ReadKey();
}
static void Main(string[] args)
{
var fender = new Product("Fender", Color.Green, Size.Small);
var gibson = new Product("Gibson", Color.Blue, Size.Large);
var martin = new Product("Martin", Color.Red, Size.Large);
Product[] products = { fender, gibson, martin };
//OLD WAY ######################################
//var pf = new ProductFilter();
//WriteLine("Green products (old):");
//foreach (var p in pf.FilterByColor(products, Color.Green))
//{
// WriteLine($" - {p.Name} is green");
//}
//NEW WAY #######################################
var bf = new BetterFilter();
WriteLine("Green products (new): ");
foreach (var p in bf.Filter(products, new ColorSpecification(Color.Green)))
{
WriteLine($" - {p.Name} is green");
}
//NEW WAY WITH COMBINATOR SPECIFICATION ###############
WriteLine("Large blue products (new): ");
foreach (var p in bf.Filter(products, new AndSpecification <Product>(new ColorSpecification(Color.Blue), new SizeSpecification(Size.Large))))
{
WriteLine($" - {p.Name} is blue and large");
}
}
private static void Main(string[] args)
{
var products = new[]
{
new Product("Coffee Table", Color.Yellow, Size.Large),
new Product("iPhone 6S", Color.Blue, Size.Small),
new Product("Tesla Model S", Color.Green, Size.Large), new Product("House", Color.Red, Size.Huge),
new Product("Chair", Color.Green, Size.Medium)
};
// WrongFilter class is an example of violation of Open / Closed principle.
// According to the principle, if we have a tested, working class, in order to
// introduce a new functionality we shall not have to modify the class, but, extend it
// by using various methods / patterns.
// In this example, WrongFilter class can perfectly filter products by their color
// or size with it's two methods. Problem arises when we need to introduce new functionality
// like "Filter by color and size". With the current iteration, we have to change WrongFilter class
// and introduce a new method to it. This violates the Open / Closed principle.
foreach (var product in WrongFilter.FilterByColor(products, Color.Green))
{
WriteLine($"{product.Name} is a {product.Color} product");
}
// With open / closed principle in mind, we created a new class called BetterFilter.
// this class implements specification pattern and instead of bringing methods for individual
// filtering actions, it introduces interfaces to define filtering specifications and a filter
// method using those specifications.
// With this approach, we can easily introduce new filtering mechanisms without ever touching BetterFilter
// class and by simply creating new ISpecification<T> implementation for requirements.
var filter = new BetterFilter();
foreach (var product in filter.Filter(products, new ColorSpecification(Color.Blue)))
{
WriteLine($"{product.Name} is a {product.Color} product");
}
// In this example we filter Green and Medium products.
foreach (var product in filter.Filter(products,
new AndSpec <Product>(new ColorSpecification(Color.Green),
new SizeSpecification(Size.Medium))))
{
WriteLine($"{product.Name} is a {product.Color} and {product.Size} product");
}
}
static void Main(string[] args)
{
Product[] products = new Product[]
{
new Product("Apple", Color.Green, Size.Small),
new Product("Tree", Color.Green, Size.Huge),
new Product("House", Color.Blue, Size.Huge)
};
var pf = new ProductFilter();
foreach (var p in pf.FilterByColor(products, Color.Green))
{
Console.WriteLine($" - {p.Name} is green");
}
var bf = new BetterFilter();
foreach (var p in bf.Filter(products, new ColorSpecificaiton(Color.Green)))
{
Console.WriteLine($" - {p.Name} is green");
}
var bf2 = new BetterFilter();
foreach (var p in bf2.Filter(products,
new AndSpecification <Product>(new ColorSpecificaiton(Color.Green), new SizeSpecification(Size.Huge))))
{
Console.WriteLine($" - {p.Name} is green and huge");
}
Console.ReadKey();
// Go to http://aka.ms/dotnet-get-started-console to continue learning how to build a console app!
}
