Model-View-Controller Framework

The Model-View-Controller (MVC) paradigm is a design pattern for creating and managing applications. It partitions the separate concerns of application data, application logic and user interface into three discrete components. It has proven to be highly successful in simplifying application design and maintenance.

The ESP Web Framework supports the Model-View-Controller pattern to enable the creation of ESP MVC applications. But it also permits you to use each component separately so that you can have stand-alone controllers, views or database models. This flexibility allows you to pick and choose the components you need or to embrace the entire MVC paradigm. You can also choose to create and render the views in the browser using a client-side Javascript MVC framework like Aurelia.

Models

The model is responsible for managing access to application data and state. It is also responsible for ensuring the data remains valid and consistent.

ESP provides a basic Object Relational Mapper (ORM) via the Embedded Database Interface (EDI). This wraps database data in a "C" language Record and Grid data structure. It then allows you to use object-oriented programming (OOP) when dealing with database data stored in rows and columns.

Views

The view is responsible for rendering the user interface and presenting the application to the user. Views should not manage incoming requests — that is the job of Controllers.

ESP provides the ESP web pages to assist in creating view web pages. ESP web pages are HTML pages with embedded "C" code. They are compiled and run to render the user interface.

Controllers

Controllers manage the application and respond to client requests. They orchestrate the application's response, they access and update model data, and display views back to the client. Incoming requests invoke Actions in the controller which modify the application state and ultimately render a view.

ESP controllers are "C" source files with one C function per action. Requests are routed by ESP by parsing and decoding request URIs and matching them with the appropriate Controller and Action function.