From ad7646860cc91f82c8b633bf662ceaccf0c873f3 Mon Sep 17 00:00:00 2001
From: "Achim D. Brucker" <adbrucker@0x5f.org>
Date: Sun, 26 Aug 2018 09:31:15 +0100
Subject: [PATCH] Added Ruby primer.

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+# DVGM -- Tips & Tricks
+
+## Helpful Ruby (on Rails) Resources
+
+- The official [Getting Started with Ruby on Rails guide](https://guides.rubyonrails.org/getting_started.html)
+- The Ruby on Rails [Security Guide](http://guides.rubyonrails.org/security.html#cross-site-request-forgery-csrf)
+- The [Ruby API search](https://apidock.com/rails/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).
+
+![Diagram of interactions within the MVC pattern.](https://en.wikipedia.org/wiki/Model%E2%80%93view%E2%80%93controller#/media/File:MVC-Process.svg)
+
+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:
+
+```csv
+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*:
+
+```SQL
+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:
+
+```csv
+login|name|grade|comment
+Peter|Security|55|I guess I should have studied more...
+Peter|Security|80|Doing the homework paid off!
+```
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