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DVGM -- Tips & Tricks
Helpful Ruby (on Rails) Resources
- The official Getting Started with Ruby on Rails guide
- The Ruby on Rails Security Guide
- The Ruby API search
Structure of the DVGM Ruby on Rails Project
DVGM, like all Ruby on Rails projects, uses the Model-View-Controller (MVC) paradigm, meaning it is decoupled into a view-part (handles the presentation to the user), a controller-part (handles the business logic of the application), and a model-part (handles the representation of the involved data and its storage).
The most important folders in the DVGM project are:
| Path | Description |
|---|---|
app |
The main directory of the app |
app/assets/javascripts |
This folder contains the CoffeeScript files that get compiled to JavaScript and sent with every page of the app. |
app/controllers |
The app controllers that contain the business logic of the app. |
app/models |
The model of the app. Ruby on Rails also automatically generates database tables from these files. |
app/views |
The HTML template files. Some views exist in multiple versions, one for each role (student/lecturer/admin) in the app. |
db/development.sqlite3 |
The database that is used by DVGM. If you want to reset the state of the app, restore this file from the repository. |
Working with DVGM
The app can be started by using bin/rails server. This will use the development
mode, which uses a local SQLite3 as a database backend and will automatically
pick-up any changes you make to the source code, so there is no need to restart
the server.
If you want to reset the database (maybe because you found a SQL Injection and
dropped all tables ;)), you can restore db/development.sqlite3 from the app source
code repository.
Lightning-Quick Introduction to SQLite3 and SQL
SQLite3 is a file-base relational database. This means that all data is stored in a single file, organized into rows and columns, where one data entry is represented by one row. For example, one student grade in DVGM is stored like this:
id|lecture_id|student_id|grade|comment|created_at|updated_at
6|7|6|55|I guess I should have studied more...|2017-04-03 09:15:57.698459|2017-04-03 09:17:05.000330
This table only does not contain the name of the student, but only a reference to them, as they are stored in a different table. Using SQL, we can look up the student and lecture names, and only display the ones for for students whose names start with a P:
SELECT login,name,grade,comment FROM users JOIN grades JOIN lectures ON users.id=student_id AND lectures.id=lecture_id WHERE login LIKE 'P% ';
The output then will look like this:
login|name|grade|comment
Peter|Security|55|I guess I should have studied more...
Peter|Security|80|Doing the homework paid off!