Creating a migration
Goal:
The suggestotron has a list of topics that people can vote on. We'll store our topics in the database. In this step you'll do the following:
- Create a database table for topics with a title and a description
In this step we'll learn a bit about MVC (Model-View-Controller) architecture. By the end of this step you should understand the following concepts:
- A record
- Model
- View
- Controller
Steps:
Try the following in your terminal:
$ rails generate scaffold topic title:string description:text
$ rake db:migrate
$ rails server
If you want, take some time to poke around the files listed in the generate step.
What Just Happened?
rails generate scaffold topic title:string description:text
generate scaffoldtells rails to create everything necessary to get up and running with topicstopictells rails the name of the new modeltitle:stringsays that topics have a title, which is a string.description:textsays that topics have a description which is a "text". (We're befuddled by the difference too).rake db:migratetells rails to update the database to include a table for our new model
Explaining MVC and Records
Rails implements a very specific notion of the Model View Controller pattern, which guides how you structure your web applications.
Model
- saves data to the database
- accesses data from the database
- bridge between the database and objects
View
- display the data for human (or machine) consumption
- webpages are views
Controller
- acts as the glue between the models and the views
- combines data from multple models
- summarizes and filters data
In MVC, models, views, and controllers have very specific jobs. Separating responsibilities like this make it easy to maintain and extend rails applications. When responsibilities become muddied it gets much harder to debug issues and add new functionality.