Forms and Views

Tour of the sample code

• Reference containing all the code: FormDemo
• Feel free to look, but DON’T COPY/PASTE! I trust you otherwise why would I give you the repo?
• Take 10 minutes now to grab the code from github and look around

Models

• There are 4 models
  • Item (Has many comments)
  • Category (Has many items)
  • Comment (Belongs to a comment)
  • Sample – IGNORE THIS ONE

Routes

• Discussion: URLs, HTTP verbs and routes
  • What’s a good URL to see all items?
  • What’s a good URL for search?
  • What’s a good URL for seeing a list of comments? Think again
  • What’s a good URL for creating a comment?
  • Let’s look at routes.rb and take turns explaining each line

Rake Tips

• rake db:migrate:reset
• rake db:seed

Let’s look: Migrations

• Nothing special going on
• Notice exactlhy ONE per table (at this stage of the game)

Let’s look: Bootstrap

• Not using any gems for now!!
• Why is most of the Bootstrap setup in application.html.erb?
• Where else do we see bootstrap?

Partials

• the _form.html.erb is a partial (view)
• the same body of the form is used in a new and update scenario
• Incorporate with render 'partial'

Seed data

• Put enough ‘real looking’ seed data so you can get a feel for the UI
• seeds.rb is a regular ruby program. Look at sample code.

How do Forms work?

Conceptual

• You need a form whenever the browser needs to send data to the server
• <form> tag begins the group of fields. It declares the URL that payload is sent to
  • There are zero or more fields
  • There’s always a “submit” link or button that triggers the sending
  • </form> terminates the group
• Sending always is done via some kind of HTTP request
  • Payload is always name=value pairs, value is always text over the wire

Rails

• There are always TWO controller actions:
  • one to display the form
  • one to accept the data from the form
  • Where can I find them for items?
  • Two controller actions means TWO urls!
• Display the form
  • Let’s look at what the HTML should look like
  • Difference between form_for and form_tag: let’s look at two examples
  • Why is there an Item.new in the form display action (new)?
• Accept data from the form
  • What URL is requested to send the data? What http verb? Why?
  • How does the data come back from the form?
  • What can the controller do with that data?
• Security issues
  • What if the form payload is not coming from your form?
  • What if your form has been modified inside the browser?
  • Explain params.require()

More complicated case

• Nested resources
  • A comment always belongs to an item
  • What should the URL look like to display the form to create a comment (THINK!) What is the verb?
  • Does the form display to add a comment work differently?
    • Using form_for vs. form_tag in this situation
  • What would the URL look like to accept the data of the new comment?
    • Let’s read the action and understand what it does
  • How do you create a nested resource, i.e. a comment for item 3?

Making Views DRY

• When you see yourself writing the same html over and over again
  • write a helper: let’s do an example!
  • write a partial: And let’s do another example!

Summary

• Routes
  • Understand the urls and verbs and how they map to controller actions
  • Use rake routes to verify your understanding
  • Make changes to routes.rb to get the urls and verbs you intend
• Forms
  • Two actions, one to display the form, one to send the payload to the server
  • form_for and form_tag are equally good. In real cases you end up with form_tag often
  • Understand params and params.require
  • Forms for nested resources
• Other tools
  • helpers to generate repetitive html
  • parials to build repetitive html
  • rake db:migrate:reset and rake db:seeds

Hacking the sample

• Get formdemo to run on your computer
• Update the new item form so it looks as pretty as the search form
• Update the search form so the options actually work
• Update the new item form so it shows a popup of categories instead of a blank