An application that actually does something¶
We introduce the Reahl basics by explaining the development of a simple address book application: it has a single page showing a list of names of people and their associated email addresses. Below the list of addresses is a means where you can add a new email address.
The home page – schematically.
This application, simple as it may seem, spans a number of development concerns that will be explained along the way:
- It has a design, and an object oriented one at that.
- It persists objects from its design into a relational database, and thus must do some form of object relational mapping.
- It displays stuff on the screen.
- It validates that input received from a user is legal; and
- It executes actions on the server in response to user actions.
Later on in the tutorial increasingly complicated variations of this simple application are used to introduce other concepts.
For now, though, this application will be built up bit by bit in these steps:
- First we build a silly model (an OO design) to show what is meant by that, and how we test models.
- Next, the model is changed (with tests) so that it can be persisted in a database.
- Then, a component is created for the app, and persisted classes registered with that component so that Reahl has the info it needs to create and maintain the underlying database schema for you.
- Some user interface fundamentals are explained next by building a simple first part of the user interface of our application using Widgets.
- Then it is time to add Input widgets (for adding a new address) to the user interface. To do that, the model is also augmented with meta information used by the user interface.
- Lastly, a “Save” Button is added to actually trigger the work server-side of adding this new address to the database.