Having completed the Sinatra section, it’s now time to build a simple Sinatra webapp.
The requirements generally focus on our ability to implement (There are other requirements not included here):
- A Model - View - Controller.
- A has_many relationship.
- Associations among tables in the database.
- User account creation and login capabilities.
- user input verification.
- Flash messages
- Forms and the routes that process user input.
The site I chose to build is an online school. A student can create an account and create programs of their choice that have different selections of topics. A student is able to select a program name and from a list of topics, select those they want to include in the program.
I first set off to build the models and establish the associations amongst the tables:
A student has many programs A program belongs to a student Each program has many topics And a topic belongs to many programs
The key in associating topics with programs is a topics_programs join table.
Building the Sinatra routes and views was relatively straight forward, once I had a basic flow working with views and routes operating as I wanted them to, I added some conditional logic to some of the views. For example, I wanted to only display the login and create users buttons on the home page if a user wasn’t already logged in. I achieved this using erb in the view file.
A pretty useful tip I learnt making this app, is to display certain things in the view based on conditional logic. I explores this concept further by combining it with error messages, in the form of Sinatra Flash.
The idea is that if a certain condition isn’t met when the route receives user input, for example a missing username from a login form, then a flash message will be set. In the corresponding view, I set up a conditional statement that checks to see if a flash message was generated. If it was, then an error was made, and so a specific error message and link is displayed. (ex: a link to go back to programs, or to login.)