B) Tutorial Overview

How to Use This Tutorial

This tutorial was developed as a step by step guide on how to use Helium and the Helium DSL to develop a sample application. The intended use is to work through the lessons in order and to use the Supplementary Documentation section as needed. The supplementary documentation also includes a list of best practices, and it's important to be aware of these before moving on from the tutorial.

All the Helium DSL features covered in the tutorial lessons are also mentioned in the DSL Reference, View Reference and Quick Reference. If more detail is needed on any topic, these documents can be consulted.

Each tutorial lesson consists of the following:

• Downloadable source code for all lessons up to that point included at the end of each lesson page as a zip file attachment. Note that although the tutorial wiki pages themselves contains some code snippets, this is mainly for demonstration/reference purposes and does not represent all the source code for the lesson. For all the source code related to a specific lesson, please refer to the downloadable zip attachment linked at the end of each lesson.

• A written lesson that highlights learning outcomes and the steps required to reach them.

Introduction to the Helium DSL

The Helium DSL is a domain specific language with Java-like syntax that runs on top of the Helium platform. The basic constructs of the language are listed in the Quick Reference.

Helium applications subscribe to the model view presenter pattern. Model components are created as Helium script files using the .mez file extension. The model files describe data validators, enum types, custom objects and relationships between objects.

Presenters are also described in .mez script files and contain variables and functions grouped together in a construct called a unit. These variables and functions contain the application logic which can be invoked in various ways.

Firstly, application logic can be invoked by views. View files contain xml and uses the .vxml file extension. Views represent the user interface where user interaction results in the execution of application logic.

In addition to views, Helium also provides special callback functions and scheduled functions which can be used to invoke code on the back-end.

The diagram below shows the model view presenter pattern that Helium apps subscribe to.

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Introduction to the Tutorial App

The application that will be developed as the base of this tutorial is an app that is centered around a seed and fertiliser store system. This system includes user management, capturing an reporting on different types of data, management of purchases, invoicing and various other notification and monitoring features.

This topic was chosen as a simplified real world example that demonstrates most, if not all, of the DSL and Helium features available to developers. The individual requirements for the application can be found below.

Lesson Plan

Conventions in This Tutorial

Where keywords, variable names, etc. from code examples or for code explanations appear in the text, it is formatted in monospace and, to distinguish further, in a particular colour: