HTTP, CRUD, REST, Routing

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HTTP, CRUD, REST, and Routing

Hypertext Transfer Protocol (HTTP)

Some Old Fashioned HTTP

Using HTTP for Client-to-server Communication

Starting Rails Server on a Different Port

To specify the port number when starting the Rails server:
```
> rails server -p 5678
```
or
```
> rails s -p 5678
```
Try starting the server on port 80, then viewing the site with a browser.

HTTP GET vs. POST

Look at the GetVsPost Example.

When using the HTTP command POST, the form information is sent to the server in the URL, for example:

http://localhost:3000/client_server/server?utf8=%E2%9C%93
    &name=Alice&gender=F&age=11&commit=Submit+Info+to+Server

Here is the generated source code for the form on the client page:

 <form accept-charset="UTF-8" action="server" method="get">

   <div style="margin:0;padding:0;display:inline">
      <input name="utf8" type="hidden" value="&#x2713;" />
   </div>

   <p>Information to be sent to server:</p>
   <p>Name:<br />
      <input id="name" name="name" type="text" value="" />
   </p>
   <p>Gender:<br />
      <input id="gender" name="gender" type="text" value="" />
   </p>
   <p>Age:<br />
      <input id="age" name="age" type="text" value="" />
   </p>
   <p>
      <input name="commit" type="submit" value="Submit Info to Server" />
   </p>
</form>

When using the HTTP command POST, the form information is sent to the server in the HTTP head section. It is not shown in the URL.

Here is the beginning of the generated HTML code for the form tag when method="post" is used. The remainder of the form, starting with "Information to be sent to the server" is the same as for method="get".

 <form accept-charset="UTF-8" action="server" method="post">
   <div style="margin:0;padding:0;display:inline">
      <input name="utf8" type="hidden" value="&#x2713;" />
      <input name="authenticity_token" type="hidden" 
         value="eTrDAIO+fK9L4KKV/KJChNebleeSIdzmgjor6VZJdss=" />
   </div>

The authenticity token is displayed in base-64 notation.

Representational State Transfer

Representational state transfer (REST) means using the HTTP commands GET, POST, PUT, and DELETE operations to implement the CRUD operations Create, Read, Update, Destroy.
REST also assumes
1. use of a client-server architecture: that processes running on the network are either clients running applications connected to the network or a servers that supply webpages or other files to clients.
2. stateless communication: that the neither the views nor the controller remember the contents of previously submitted pages.
Defining the following route in config/routes.rb creates the entire set of CRUD operations:
```
resources :items
```
Table of RESTful Routes, when the resources are defined as :owners.

Helper Methods for URLs

Here are some Rails helper methods generated by the Rails scaffold software from the student table for use by the link_to method:

Action Helper Method that Generates a URL path

index students_path

show student*

new new_student_path

edit edit_student_path

destroy student*

*For the show and destroy actions, a helper method is not needed. The object variable student is passed directly to the link_to method.
Built a scaffold based Rails project with
```
> rails new School
> cd School
> rails g scaffold Student name:string ⇓
     year:integer birth_date:date gpa:float
```
(⇓ means don't press the enter key when entering in the CommandPrompt Window.)

Action	Helper Method that Generates a URL path
index	students_path
show	student*
new	new_student_path
edit	edit_student_path
destroy	student*

Here are some links from the Student example:

<%= link_to 'Show', student %>

<%= link_to 'Back', students_path %>

<%= link_to 'New Student', new_student_path %>

<%= link_to 'Edit', edit_student_path(student) %>

<%= link_to 'Destroy', student, 
                :confirm => 'Are you sure?',
                :method => :delete %>

Routing

Routes are specified in the file app/config/routes.rb.
So far, the Rails applications we have created have used named routes.
For example, if the controller name is Info and the view name is staff, then the named route used to view this page is
```
get "info/staff"
```
A project created using a scaffold uses a resource based route:
```
resources :movie_reviews
```