The most basic Chain of Responsibility starts by defining an interface that handles a request (IHandler). Then we add classes that handle one or more scenarios (Handler1 and Handler2): Figure 12.2: Class diagram representing the Chain of Responsibility pattern A difference between the Chain of Responsibility pattern and many other patterns is that no central […]
Conclusion – Behavioral Patterns
The Template Method is a powerful and easy-to-implement design pattern allowing subclasses to reuse the algorithm’s skeleton while implementing (abstract) or overriding (virtual) subparts. It allows implementation-specific classes to extend the core algorithm. It can reduce the duplication of logic and improve maintainability while not cutting out any flexibility in the process. There are many […]
Project – Building a search machine – Behavioral Patterns-2
Now that we have defined the actors and explored the code, let’s see what is happening in our consumer (the Client): The Find method returns null when it does not find a value and, by extension, the IndexOf method.By running the program, we get the following output: =============================================Current search machine is LinearSearchMachineThe element ‘1’ was […]
Project – Building a search machine – Behavioral Patterns-1
Let’s start with a simple, classic example to demonstrate how the Template Method pattern works.Context: Depending on the collection, we want to use a different search algorithm. We want to use a binary search for sorted collections, but we want to use a linear search for unsorted collections.Let’s start with the consumer, a REST endpoint […]
The program – Structural Patterns
Now, let’s analyze the consumer, an ASP.NET Core application that forwards HTTP requests to the façades and return the result as their response.The first step is to register the dependencies like this: var builder = WebApplication.CreateBuilder(args);builder.Services .AddOpaqueFacadeSubSystem() .AddTransparentFacadeSubSystem(); With these extension methods, the application root is so clean that it is hard to know that […]
Transparent façade – Structural Patterns
The transparent façade is the most flexible type of façade and is exceptionally suitable for a system that leverages dependency injection. The implementation is similar to the opaque façade, but the public visibility modifier changes how consumers can access the class library elements. For this system, it was worth adding interfaces to allow the consumers […]
Project – The façades – Structural Patterns
In this example, we play with the following C# projects: Let’s start with the class libraries. To follow the SOLID principles, adding some interfaces representing the elements of the subsystem seemed appropriate. In subsequent chapters, we explore how to organize our abstractions to be more reusable, but for now, both abstractions and implementations are in […]
Implementing the Façade design pattern – Structural Patterns
The Façade pattern is a structural pattern that simplifies the access to a complex system. It is very similar to the Adapter pattern, but it creates a wall (a façade) between one or more subsystems. The big difference between the adapter and the façade is that instead of adapting an interface to another, the façade […]
Project – Greeter – Structural Patterns
Context: We’ve programmed a highly sophisticated greeting system that we want to reuse in a new program. However, its interface does not match the new design, and we cannot modify it because other systems use that greeting system.To fix this problem, we decided to apply the Adapter pattern. Here is the code of the external […]
Project – BookStore – Structural Patterns-3
In the preceding Create method, we create the corporation, add two stores, then return the result.The CreateTaleTowersStore and CreateEpicNexusStore methods create a store, set their name, address, and manager, and create three sections each: private IComponent CreateTaleTowersStore(){ var store = new Store( “Tale Towers”, “125 Enchantment Street, Storyville, SV 72845”, “Malcolm Reynolds” ); store.Add(CreateFantasySection()); store.Add(CreateAdventureSection()); […]