Rails program runs with unexpected results

When it comes to Rails, try to follow the flow of your program.

Most http requests follow this flow:

1. The browser sends the request to the server (if you're issue is happening while developing, then the browser is likely sending the request to IP Address 127.0.0.1 (localhost), TCP Port 3000.

2. Rails looks up the request in its Routing table

3. Rails sends the request on to the appropriate Controller

4. Rails invokes the appropriate Action (aka method) in the Controller

5. Your Controller Method uses Model(s)

6. Your Models communicate with the Database

7. Your Controller Method renders a View and Layout

8. The response is send back to the browser

How To Fix

Step 1. Identify the HTTP request method being sent:

GET - if the URL was entered into a browser's location bar and enter was pressed, or if a regular link was clicked

POST - if a form submit button was clicked to create a new record

PUT & PATCH - if a form submit button was clicked to update an existing record

DELETE - if a link with the method set to delete was clicked

Step 2. Identify the path of the HTTP request:

Take a look at the URL being sent:

For GET requests: the URL will be in the browser's location bar.

For POST, PUT and PATCH requests: you can see the URL by using debugging tools to inspect the <form> tag. Within the <form> form tag is an action attribute. This will be set to the URL or PATH.

For DELETE requests, inspect the delete link using debugging tools and look at the href attribute.

A URL is made up of several parts:

• Protocol: http or https
• Hostname: localhost
• Port number: 80 or 3000 (sometimes this isn't visible)
• Path: the segment between the Hostname/Post Number up until either the end of the URL, or until the first ?, whichever comes first. Note the the path can also be empty if nothing follows the Hostname/Post Number
• Parameters: everything that follows the ? (not necessarily present)

e.g.

• http://localhost:3000/products/new - the path is products/new
• http://localhost:3000/ - the path is empty
• http://localhost:3000/search?q=my+search+terms - the path is search

Step 3. Match the http request method and path with the route

Take a look at your routes using:

rails routes

on the command line.

You should see something like this:

      Prefix Verb   URI Pattern                  Controller#Action
    products GET    /products(.:format)          products#index
             POST   /products(.:format)          products#create
 new_product GET    /products/new(.:format)      products#new
edit_product GET    /products/:id/edit(.:format) products#edit
     product GET    /products/:id(.:format)      products#show
             PATCH  /products/:id(.:format)      products#update
             PUT    /products/:id(.:format)      products#update
             DELETE /products/:id(.:format)      products#destroy

Match the HTTP Request Method you obtained in the previous step with the VERB column.

Match the PATH you obtained in the previous step with the URI Pattern column:

When matching against a URI Pattern, break the Pattern into segments, with each segment being in between two slashes. For example:

/products/new - products is one segment, new is another segment.

Figure out if each segment is a static or dynamic segment:

• static segments do not begin with a : (colon)
• dynamic segments begin with a : (colon)

Match each segment with the PATH:

• static segments need to match exactly
• dynamic segments are wildcards, and can match against anything

note: you can ignore the (.:format) portion of the URI Pattern for regular web page requests.

Example 1

http://localhost:3000/products matches:

  Prefix Verb   URI Pattern                  Controller#Action
products GET    /products(.:format)          products#index

Example 2

http://localhost:3000/products/99 matches:

  Prefix Verb   URI Pattern                  Controller#Action
 product GET    /products/:id(.:format)      products#show

Step 4. Match the route with the appropriate controller and action

Now that you know the route, look at the Controller#Action column to see what controller and what method is being invoked.

For example, if you identified the following route as matching:

  Prefix Verb   URI Pattern                  Controller#Action
products GET    /products(.:format)          products#index

Then you would open the ProductsController and go to def index.