Last week, in order to create a Create command for an entity, I first needed to create four components: CreateCommand, CreateCommandHandler, CreateCommandResponse, and CreateCommandValidator.
CreateCommand represents the command itself and contains all the necessary data required to create a new entity in the system, including things like the entity’s name, description, and other important details. This was where I also learned something new about using a question mark when defining a property (e.g., public int? Age { get; set; }). The “?” symbol allows the property to be set to null if no information is available.
Next, I created the CreateCommandHandler, which is responsible for handling the CreateCommand and performing the necessary actions to create the entity in the system. It receives the CreateCommand, validates the data, and creates the entity in the appropriate data store. This part of the code (CreateCommandHandler) was challenging for me because I wasn’t sure what code to write, but Mr. Peter helped me understand by using an example from a previous entity. He also pointed out that my difficulty was due to not fully grasping OOP principles.
Then, there’s the CreateCommandResponse, which is the component returned by the CreateCommandHandler after the entity has been successfully created. It contains the ID or other relevant information about the newly created entity. Moving on to next week, I’ll be continuing on creating another component named CreateCommandValidator, which is responsible for validating the data in the CreateCommand before it is processed by the CreateCommandHandler. This component ensures that the data is in the correct format and meets any required constraints.
Together, these four components create a system that is capable of creating new entities within a CQRS-based system. CreateCommand encapsulates all the necessary data, CreateCommandHandler creates the entity, CreateCommandResponse provides information about the newly created entity, and CreateCommandValidator ensures that the data is valid before it is processed.