CSC/ECE 517 Fall 2012/ch1b 1w66 as

Forms-Ruby

Introduction

Forms in web applications are an essential interface for user input. However, form markup can quickly become tedious to write and maintain because of form control naming and their numerous attributes. Rails deals away with these complexities by providing view helpers for generating form markup.<ref>http://www.guides.rubyonrails.org/form_helpers.html</ref> Rails provides excellent features to create forms and gather user input. Forms in Rails are an effective way to obtain user input in a convenient manner. Forms can include different types of data fields that will help obtain different types of data. For example, Text box can fetch a few words from the user and Text Area, a paragraph. Forms are embedded in a Web Application and are very user-friendly. Forms in Rails also have in-built functionalities to verify the data the user enters, validate it using a set of predefined rules, display corresponding error messages(in case of non-compliance) and storing the information in the database if it passes validation.

Creating a Form

Forms written in Rails are automatically generated as HTML Forms and are rendered into views. Forms are created in Rails using the basic helper called Form_tag

<%= form_tag do %>
  Form contents
<% end %>

When form_tag is called as above, it creates a <form> tag which, when submitted, will POST to the current page. For instance, assuming the current page is /home/index, the generated HTML will look like this (some line breaks added for readability): <ref>http://edgeguides.rubyonrails.org/form_helpers.html#making-select-boxes-with-ease</ref>

<form accept-charset="UTF-8" action="/home/index" method="post">
  <div style="margin:0;padding:0">
    <input name="utf8" type="hidden" value="✓" />
    <input name="authenticity_token" type="hidden" value="f755bb0ed134b76c432144748a6d4b7a7ddf2b71" />
  </div>
  Form contents
</form>

Forms in Rails consist of Elements, which are labels, input elements, submit buttons etc.

Text Fields

Text Fields in Rails Forms allow the user to input a few words or a single word. These are generally used to capture Names, Addresses, Phone numbers etc. To create a text field in Rails Forms use the following syntax:<ref>http://www.tutorialspoint.com/ruby-on-rails/rails-html-forms.htm</ref>

<%= text_field :modelname, :attribute_name, options %>

In the example below we create a text field of size 20 characters :

<%= text_field "person", "name", "size" => 20 %>

This will generate following code:

<input type="text" id="person_name" name="person[name]"
      size="20" value="<%= @person.name %>" />

Rails also allows us to create Hidden Fields. Hidden Fields don't show up on the Page and hence can contain any value which the user cannot see or change. To create hidden fields use the following syntax;

<%= hidden_field ... %>

To create password fields use the following syntax;

<%= password_field ... %>

To create file upload fields use the following syntax;

<%= file_field ... %>

TextArea Fields

Text Area Fields allow us to enter information in paragraphs, i.e, enter data that has more than a few words and sentences. Text Area Fields are also adjustable in size. To change the size of a Text Area Field, we are required to change the rows and cols values to numbers of our interest. <ref>http://www.tutorialspoint.com/ruby-on-rails/rails-html-forms.htm</ref> To create a text area use the following syntax:

<%= text_area ... %>

Example:

<%= text_area "post", "body", "cols" => 20, "rows" => 40%>

This will generate the following code:

<textarea cols="20" rows="40" id="post_body" name="post[body]">
<%={@post.body}%>
</textarea>

Radio Button

Rails Forms can also include Radio Button, for choice based User Inputs.

To create a Radio Button use the following syantax:

<%= radio_button :modelname, :attribute, :tag_value, options %>

Consider example:

 radio_button("post", "category", "rails")
 radio_button("post", "category", "java")

This will generate following code:

<input type="radio" id="post_category" name="post[category]" 
value="rails" checked="checked" />
<input type="radio" id="post_category" name="post[category]" 
                    value="java"= />

Checkbox Button

Checkboxes can be added to Forms in Rails, using the following syntax<ref>http://www.tutorialspoint.com/ruby-on-rails/rails-html-forms.htm</ref>

<%= check_box :modelname, :attribute,options,on_value,off_value%>

Consider the following example:

check_box("post", "validated")

This generate following code:

<input type="checkbox" id="post_validate" name="post[validated]" 
                                   value="1" checked="checked" />
<input name="post[validated]" type="hidden" value="0" />

Dropdown List

Dropdown Lists in Forms allow users to select a value from a set of predefined values. To create a dropdown list use the following syntax:

<%= select :variable,:attribute,choices,options,html_options%

Have a look at the following example:

select("post", "person_id", 
       Person.find(:all).collect {|p| [ p.name, p.id ] })
This could generate following code. It depends on what value is available in your database.:
  <select name="post[person_id]">
    <option value="1">David</option>
    <option value="2">Sam</option>
    <option value="3">Tobias</option>
  </select>

The Submit Button

The Submit Button: Submit button in Rails will perform the desired action the form is linked to, and is usually located in the bottom, where the form ends. Submit button sends the data in the form through POST/GET actions in HTML.

Actions

The action attribute in Rails Forms specifies what to do when a Form is submitted<ref>http://paulsturgess.co.uk/articles/49-using-helper-methods-in-ruby-on-rails</ref>. The action attribute is specified in form_tag itself. For example,

  <%= form_tag :action => "create" %>
   Name: <%= text_field "item", "name"
%><br />
   Value: <%= text_field "item", "value"
%><br />
   <%= submit_tag %>
  <%= end_form_tag %>

For the object "item" in the example above, the Controller ItemsController should include a method called "create" which will respond to the form's action. We add the method "Create" in the code below:

class ItemsController < ApplicationController
    def new
      @item = Item.new
    end
#add method create
    def create
      @item = Item.create(params[:item]) 
      redirect_to :action => 'edit', :id => @item.id 
    end
#add method create
  end

If more actions are desired, corresponding methods must be added in the Controller class of the object.

References

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