240 lines
9.8 KiB
Text
240 lines
9.8 KiB
Text
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= Application Extensions and Helpers (padrino-helpers)
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=== Overview
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This component provides a great deal of view helpers related to html markup generation.
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There are helpers for generating tags, forms, links, images, and more. Most of the basic
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methods should be very familiar to anyone who has used rails view helpers.
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=== Output Helpers
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Output helpers are a collection of important methods for managing, capturing and displaying output
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in various ways and is used frequently to support higher-level helper functions. There are
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three output helpers worth mentioning: <tt>content_for</tt>, <tt>capture_html</tt>, and <tt>concat_content</tt>
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The content_for functionality supports capturing content and then rendering this into a different place
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such as within a layout. One such popular example is including assets onto the layout from a template:
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# app/views/site/index.erb
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...
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<% content_for :assets do %>
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<%= stylesheet_link_tag 'index', 'custom' %>
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<% end %>
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...
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Added to a template, this will capture the includes from the block and allow them to be yielded into the layout:
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# app/views/layout.erb
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...
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<head>
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<title>Example</title>
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<%= stylesheet_link_tag 'style' %>
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<%= yield_content :assets %>
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</head>
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...
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This will automatically insert the contents of the block (in this case a stylesheet include) into the
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location the content is yielded within the layout. You can also check if content exists for a block using
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<tt>content_for?(true)</tt> which returns true if content exists.
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The capture_html and the concat_content methods allow content to be manipulated and stored for use in building
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additional helpers accepting blocks or displaying information in a template. One example is the use of
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these in constructing a simplified 'form_tag' helper which accepts a block.
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# form_tag '/register' do ... end
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def form_tag(url, options={}, &block)
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# ... truncated ...
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inner_form_html = capture_html(&block)
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concat_content '<form>' + inner_form_html + '</form>'
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end
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This will capture the template body passed into the form_tag block and then append the content
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to the template through the use of <tt>concat_content</tt>. Note have been built to work for both haml and erb
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templates using the same syntax.
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For more information on using output helpers, check out the guide for
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{Padrino Helpers}[http://www.padrinorb.com/guides/application-helpers].
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=== Tag Helpers
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Tag helpers are the basic building blocks used to construct html 'tags' within a view template. There
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are three major functions for this category: <tt>tag</tt>, <tt>content_tag</tt> and <tt>input_tag</tt>.
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The tag and content_tag are for building arbitrary html tags with a name and specified options. If
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the tag contains 'content' within then <tt>content_tag</tt> is used. For example:
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tag(:br, :style => 'clear:both') => <br style="clear:both" />
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content_tag(:p, "demo", :class => 'light') => <p class="light">demo</p>
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The input_tag is used to build tags that are related to accepting input from the user:
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input_tag :text, :class => "demo" => <input type='text' class='demo' />
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input_tag :password, :value => "secret", :class => "demo"
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Note that all of these accept html options and result in returning a string containing html tags.
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For more information on using tag helpers, check out the guide for
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{Padrino Helpers}[http://www.padrinorb.com/guides/application-helpers].
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=== Asset Helpers
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Asset helpers are intended to help insert useful html onto a view template such as 'flash' notices,
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hyperlinks, mail_to links, images, stylesheets and javascript. An example of their uses would be on a
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simple view template:
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# app/views/example.haml
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...
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%head
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= stylesheet_link_tag 'layout'
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= javascript_include_tag 'application'
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%body
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...
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= flash_tag :notice
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%p= link_to 'Blog', '/blog', :class => 'example'
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%p Mail me at #{mail_to 'fake@faker.com', "Fake Email Link", :cc => "test@demo.com"}
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%p= image_tag 'padrino.png', :width => '35', :class => 'logo'
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For more information on using asset helpers, check out the guide for
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{Padrino Helpers}[http://www.padrinorb.com/guides/application-helpers].
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=== Form Helpers
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Form helpers are the 'standard' form tag helpers you would come to expect when building forms. A simple
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example of constructing a non-object form would be:
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- form_tag '/destroy', :class => 'destroy-form', :method => 'delete' do
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= flash_tag(:notice)
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- field_set_tag do
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%p
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= label_tag :username, :class => 'first'
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= text_field_tag :username, :value => params[:username]
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%p
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= label_tag :password, :class => 'first'
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= password_field_tag :password, :value => params[:password]
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%p
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= label_tag :strategy
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= select_tag :strategy, :options => ['delete', 'destroy'], :selected => 'delete'
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%p
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= check_box_tag :confirm_delete
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- field_set_tag(:class => 'buttons') do
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= submit_tag "Remove"
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For more information on using form helpers, check out the guide for
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{Padrino Helpers}[http://www.padrinorb.com/guides/application-helpers].
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=== FormBuilders
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Form builders are full-featured objects allowing the construction of complex object-based forms
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using a simple, intuitive syntax.
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A form_for using these basic fields might look like:
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- form_for @user, '/register', :id => 'register' do |f|
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= f.error_messages
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%p
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= f.label :username, :caption => "Nickname"
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= f.text_field :username
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%p
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= f.label :email
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= f.text_field :email
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%p
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= f.label :password
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= f.password_field :password
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%p
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= f.label :is_admin, :caption => "Admin User?"
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= f.check_box :is_admin
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%p
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= f.label :color, :caption => "Favorite Color?"
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= f.select :color, :options => ['red', 'black']
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%p
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- fields_for @user.location do |location|
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= location.text_field :street
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= location.text_field :city
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%p
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= f.submit "Create", :class => 'button'
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Forms can also accept nested attributes using `fields_for` within the form builder in recent releases. Check out the guide for {Padrino Helpers}[http://www.padrinorb.com/guides/application-helpers] to learn more about nested forms.
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There is also an additional StandardFormBuilder which builds on the abstract fields that can be used within a form_for.
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A form_for using these standard fields might be:
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- form_for @user, '/register', :id => 'register' do |f|
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= f.error_messages
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= f.text_field_block :name, :caption => "Full name"
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= f.text_field_block :email
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= f.check_box_block :remember_me
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= f.select_block :fav_color, :options => ['red', 'blue']
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= f.password_field_block :password
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= f.submit_block "Create", :class => 'button'
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and would generate this html (with each input contained in a paragraph and containing a label):
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<form id="register" action="/register" method="post">
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<p><label for="user_name">Full name: </label><input type="text" id="user_name" name="user[name]"></p>
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...omitted...
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<p><input type="submit" value="Create" class="button"></p>
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</form>
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You can also easily build your own FormBuilder which allows for customized fields and behavior.
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For more information on using the Padrino form builders, check out the guide for
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{Padrino Helpers}[http://www.padrinorb.com/guides/application-helpers].
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=== Format Helpers
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Format helpers are several useful utilities for manipulating the format of text to achieve a goal.
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The four format helpers are <tt>escape_html</tt>, <tt>time_ago_in_words</tt>, and <tt>js_escape_html</tt>.
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The escape_html and js_escape_html function are for taking an html string and escaping certain characters.
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<tt>escape_html</tt> will escape ampersands, brackets and quotes to their HTML/XML entities. This is useful
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to sanitize user content before displaying this on a template. <tt>js_escape_html</tt> is used for
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passing javascript information from a js template to a javascript function.
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escape_html('<hello>&<goodbye>') # => <hello>&<goodbye>
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There is also an alias for escape_html called <tt>h</tt> for even easier usage within templates.
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Format helpers also includes a number of useful text manipulation functions such as <tt>simple_format</tt>,
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<tt>pluralize</tt>, <tt>word_wrap</tt>, <tt>truncate</tt> and <tt>truncate_words</tt>.
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simple_format("hello\nworld") # => "<p>hello<br/>world</p>"
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pluralize(2, 'person') => '2 people'
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word_wrap('Once upon a time', :line_width => 8) => "Once upon\na time"
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truncate("Once upon a time in a world far far away", :length => 8) => "Once upon..."
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truncate_words("Once upon a time in a world far far away", :length => 4) => "Once upon a time..."
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These helpers can be invoked from any route or view within your application.
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For more information on using the format helpers, check out the guide for
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{Padrino Helpers}[http://www.padrinorb.com/guides/application-helpers].
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=== Render Helpers
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This component provides a number of rendering helpers making the process of displaying templates a bit easier.
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This plugin also has support for useful additions such as partials (with support for :collection) for the templating system.
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Using render plugin helpers is extremely simple. If you want to render an erb template in your view path:
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render :erb, 'path/to/erb/template'
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or using haml templates works just as well:
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render :haml, 'path/to/haml/template'
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There is also a method which renders the first view matching the path and removes the need to define an engine:
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render 'path/to/any/template'
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Finally, we have the all-important partials support for rendering mini-templates onto a page:
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partial 'photo/_item', :object => @photo, :locals => { :foo => 'bar' }
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partial 'photo/_item', :collection => @photos
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For more information on using the render and partial helpers, check out the guide for
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{Padrino Helpers}[http://www.padrinorb.com/guides/application-helpers].
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== Copyright
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Copyright (c) 2011 Padrino. See LICENSE for details.
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