9/30/15

IT 232 -- 9/30/15

Review Question

Suppose that the primary model is User and the secondary model is Photo. Convert these resource based routes to nested routes:

Current View	Target View	Helper Method	Answers
index	show	photo_path(photo)	user_photo_path(@user, photo)
index	edit	edit_photo_path(photo)	edit_user_photo_path(@user, photo)
index	new	new_photo_path	new_user_photo_path(@user)
show	edit	photo_path(@photo)	edit_user_photo_path(@user, @photo)
show	index	photo_path(@photo)	user_photos_path(@user)
edit	show	photo_path(@photo)	user_photo_path(@user, @photo)

Use the RESTful Routes tables to help you.

Regular Expressions

A regular expression is a text string that describes which input strings are allowed (accepted) and which are not allowed.
Regular expressions can be used in Rails validations.
Here is a table of some common regular expression tokens.
Practice Exercises:
1. What are regular expressions and how are they used?
2. Test out these regular expressions on this Rubilar website:
  1. U.S. zipcode.
  2. U.S. phone number.
  3. Ruby integer constant.
Use a regular expression to validate a phone number in a Rails scaffold project. Here are Some Rails Validations to help you out.

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>
</form>

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.
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
```
Some details of REST operations, when the resources are defined as :items.
To see all the defined routes for a Rails project, type rake routes in the Command Prompt Window.

Adding an Action to a Scaffold Based Project

We already know how to add an action to a non-scaffold based controller.
An easy way to add a new action is to create a new non-scaffold based controller and add the new action there.
An action is a method in a controller that is executed.
Look at the AddAction Example.

Rendering in Web Service Format

Normally, a Rails scaffold application shows its output in HTML format, which is designed to be human readable. Try these URLs for the Hospital Example:
```
http://localhost:3000/patients
http://localhost:3000/patients/3
```
A web service produces output in a format designed to be consumed by another computer. A popular output format for a web service is JSON. These URLs produce JSON output that can be saved or passed to another application:
```
http://localhost:3000/patients.json
http://localhost:3000/patients/3.json
```
JSON format is similar to a Ruby array of Hash objects.

To obtain the output in XML format, add code to the index and show methods of the patients controller like this:

 # GET /patients
# GET /patients.json
def index
  @patients = Patient.all

  # Insert code here:
  respond_to do |format|
    format.html
    format.xml { render xml: @patients }
  end
  # End of inserted code.

end

# GET /patients/1
# GET /patients/1.json
def show

  # Insert code here:
  respond_to do |format|
    format.html
    format.xml { render xml: @patient }
  end
  # End of inserted code.

end

Now obtain XML output with these URLs:

http://localhost:3000/patients.xml
http://localhost:3000/patients/3.xml

Forms and Controls

FormHelper vs. FormTagHelper Methods

Use this source code to construct a temperature converter application:

------- Controller ------------------
class ConvertController < ApplicationController
  def input
    @c = 0
  end

  def display
    @c = params[:cel].to_i
    @f = 9 * @c / 5 + 32
  end
end

-------- input view --------------------
<h1>Temperature Converter</h1>

<%= form_tag 'display' do %>
  <p><%= text_field_tag :cel, @c.to_s %></p>
  <p><%= submit_tag 'Convert' %></p>
<% end %>

-------- display view ------------------
<h1>Temperature Converter</h1>

<p>Celsius: <%= @c %></p>
<p>Fahrenheit: <%= @f %></p>
<p><%= link_to "Input Page", convert_input_path %></p>

-------- routes file
Rails.application.routes.draw do
  get 'convert/input'
  get 'convert/display'
  post 'convert/display'
end

Rails Relationships

http://guides.rubyonrails.org/association_basics.html