Module | ActionView::Helpers::UrlHelper
In: | lib/action_view/helpers/url_helper.rb

Provides a set of methods for making links and getting URLs that depend on the routing subsystem (see ActionController::Routing). This allows you to use the same format for links in views and controllers.

### Methods

button_to current_page? link_to link_to_if link_to_unless link_to_unless_current mail_to url_for

### Included Modules

JavaScriptHelper

### Public Instance methods

button_to(name, options = {}, html_options = {})

Generates a form containing a single button that submits to the URL created by the set of `options`. This is the safest method to ensure links that cause changes to your data are not triggered by search bots or accelerators. If the HTML button does not work with your layout, you can also consider using the link_to method with the `:method` modifier as described in the link_to documentation.

The generated FORM element has a class name of `button-to` to allow styling of the form itself and its children. You can control the form submission and input element behavior using `html_options`. This method accepts the `:method` and `:confirm` modifiers described in the link_to documentation. If no `:method` modifier is given, it will default to performing a POST operation. You can also disable the button by passing `:disabled => true` in `html_options`. If you are using RESTful routes, you can pass the `:method` to change the HTTP verb used to submit the form.

#### Options

The `options` hash accepts the same options at url_for.

There are a few special `html_options`:

- `:method` - Specifies the anchor name to be appended to the path.
- `:disabled` - Specifies the anchor name to be appended to the path.
- `:confirm` - This will add a JavaScript confirm prompt with the question specified. If the user accepts, the link is processed normally, otherwise no action is taken.

#### Examples

      <%= button_to "New", :action => "new" %>
      # => "<form method="post" action="/controller/new" class="button-to">
      #      <div><input value="New" type="submit" /></div>
      #    </form>"

      button_to "Delete Image", { :action => "delete", :id => @image.id },
                :confirm => "Are you sure?", :method => :delete
      # => "<form method="post" action="/images/delete/1" class="button-to">
      #      <div>
      #        <input type="hidden" name="_method" value="delete" />
      #        <input onclick="return confirm('Are you sure?');"
      #              value="Delete" type="submit" />
      #      </div>
      #    </form>"

current_page?(options)

True if the current request URI was generated by the given `options`.

#### Examples

Let‘s say we‘re in the `/shop/checkout?order=desc` action.

      current_page?(:action => 'process')
      # => false

      current_page?(:controller => 'shop', :action => 'checkout')
      # => true

      current_page?(:controller => 'shop', :action => 'checkout', :order => 'asc')
      # => false

      current_page?(:action => 'checkout')
      # => true

      current_page?(:controller => 'library', :action => 'checkout')
      # => false

Let‘s say we‘re in the `/shop/checkout?order=desc&page=1` action.

      current_page?(:action => 'process')
      # => false

      current_page?(:controller => 'shop', :action => 'checkout')
      # => true

      current_page?(:controller => 'shop', :action => 'checkout', :order => 'desc', :page=>'1')
      # => true

      current_page?(:controller => 'shop', :action => 'checkout', :order => 'desc', :page=>'2')
      # => false

      current_page?(:controller => 'shop', :action => 'checkout', :order => 'desc')
      # => false

      current_page?(:action => 'checkout')
      # => true

      current_page?(:controller => 'library', :action => 'checkout')
      # => false

link_to(*args, &block)

Creates a link tag of the given `name` using a URL created by the set of `options`. See the valid options in the documentation for url_for. It‘s also possible to pass a string instead of an options hash to get a link tag that uses the value of the string as the href for the link, or use `:back` to link to the referrer - a JavaScript back link will be used in place of a referrer if none exists. If nil is passed as a name, the link itself will become the name.

#### Signatures

      link_to(name, options = {}, html_options = nil)
      link_to(options = {}, html_options = nil) do
        # name
      end

#### Options

- `:confirm => ‘question?‘` - This will add a JavaScript confirm prompt with the question specified. If the user accepts, the link is processed normally, otherwise no action is taken.
- `:popup => true || array of window options` - This will force the link to open in a popup window. By passing true, a default browser window will be opened with the URL. You can also specify an array of options that are passed-thru to JavaScripts window.open method.
- `:method => symbol of HTTP verb` - This modifier will dynamically create an HTML form and immediately submit the form for processing using the HTTP verb specified. Useful for having links perform a POST operation in dangerous actions like deleting a record (which search bots can follow while spidering your site). Supported verbs are `:post`, `:delete` and `:put`. Note that if the user has JavaScript disabled, the request will fall back to using GET. If you are relying on the POST behavior, you should check for it in your controller‘s action by using the request object‘s methods for `post?`, `delete?` or `put?`.
- The `html_options` will accept a hash of html attributes for the link tag.

Note that if the user has JavaScript disabled, the request will fall back to using GET. If `:href => ’#’` is used and the user has JavaScript disabled clicking the link will have no effect. If you are relying on the POST behavior, your should check for it in your controller‘s action by using the request object‘s methods for `post?`, `delete?` or `put?`.

You can mix and match the `html_options` with the exception of `:popup` and `:method` which will raise an ActionView::ActionViewError exception.

#### Examples

Because it relies on `url_for`, `link_to` supports both older-style controller/action/id arguments and newer RESTful routes. Current Rails style favors RESTful routes whenever possible, so base your application on resources and use

      link_to "Profile", profile_path(@profile)
      # => <a href="/profiles/1">Profile</a>

or the even pithier

      link_to "Profile", @profile
      # => <a href="/profiles/1">Profile</a>

in place of the older more verbose, non-resource-oriented

      link_to "Profile", :controller => "profiles", :action => "show", :id => @profile
      # => <a href="/profiles/show/1">Profile</a>

Similarly,

      link_to "Profiles", profiles_path
      # => <a href="/profiles">Profiles</a>

is better than

      link_to "Profiles", :controller => "profiles"
      # => <a href="/profiles">Profiles</a>

You can use a block as well if your link target is hard to fit into the name parameter. ERb example:

      <% link_to(@profile) do %>
        <strong><%= @profile.name %></strong> -- <span>Check it out!!</span>
      <% end %>
      # => <a href="/profiles/1"><strong>David</strong> -- <span>Check it out!!</span></a>

Classes and ids for CSS are easy to produce:

      link_to "Articles", articles_path, :id => "news", :class => "article"
      # => <a href="/articles" class="article" id="news">Articles</a>

Be careful when using the older argument style, as an extra literal hash is needed:

      link_to "Articles", { :controller => "articles" }, :id => "news", :class => "article"
      # => <a href="/articles" class="article" id="news">Articles</a>

Leaving the hash off gives the wrong link:

      link_to "WRONG!", :controller => "articles", :id => "news", :class => "article"
      # => <a href="/articles/index/news?class=article">WRONG!</a>

`link_to` can also produce links with anchors or query strings:

      link_to "Comment wall", profile_path(@profile, :anchor => "wall")
      # => <a href="/profiles/1#wall">Comment wall</a>

      link_to "Ruby on Rails search", :controller => "searches", :query => "ruby on rails"
      # => <a href="/searches?query=ruby+on+rails">Ruby on Rails search</a>

      link_to "Nonsense search", searches_path(:foo => "bar", :baz => "quux")
      # => <a href="/searches?foo=bar&amp;baz=quux">Nonsense search</a>

The three options specific to `link_to` (`:confirm`, `:popup`, and `:method`) are used as follows:

      link_to "Visit Other Site", "http://www.rubyonrails.org/", :confirm => "Are you sure?"
      # => <a href="http://www.rubyonrails.org/" onclick="return confirm('Are you sure?');">Visit Other Site</a>

      link_to "Help", { :action => "help" }, :popup => true
      # => <a href="/testing/help/" onclick="window.open(this.href);return false;">Help</a>

      link_to "View Image", @image, :popup => ['new_window_name', 'height=300,width=600']
      # => <a href="/images/9" onclick="window.open(this.href,'new_window_name','height=300,width=600');return false;">View Image</a>

      link_to "Delete Image", @image, :confirm => "Are you sure?", :method => :delete
      # => <a href="/images/9" onclick="if (confirm('Are you sure?')) { var f = document.createElement('form');
           f.style.display = 'none'; this.parentNode.appendChild(f); f.method = 'POST'; f.action = this.href;
           var m = document.createElement('input'); m.setAttribute('type', 'hidden'); m.setAttribute('name', '_method');
           m.setAttribute('value', 'delete'); f.appendChild(m);f.submit(); };return false;">Delete Image</a>

link_to_if(condition, name, options = {}, html_options = {}, &block)

Creates a link tag of the given `name` using a URL created by the set of `options` if `condition` is true, in which case only the name is returned. To specialize the default behavior, you can pass a block that accepts the name or the full argument list for link_to_unless (see the examples in link_to_unless).

#### Examples

      <%= link_to_if(@current_user.nil?, "Login", { :controller => "sessions", :action => "new" }) %>
      # If the user isn't logged in...
      # => <a href="/sessions/new/">Login</a>

      <%=
         link_to_if(@current_user.nil?, "Login", { :controller => "sessions", :action => "new" }) do
           link_to(@current_user.login, { :controller => "accounts", :action => "show", :id => @current_user })
         end
      %>
      # If the user isn't logged in...
      # => <a href="/sessions/new/">Login</a>
      # If they are logged in...
      # => <a href="/accounts/show/3">my_username</a>

link_to_unless(condition, name, options = {}, html_options = {}) {|name| ...}

Creates a link tag of the given `name` using a URL created by the set of `options` unless `condition` is true, in which case only the name is returned. To specialize the default behavior (i.e., show a login link rather than just the plaintext link text), you can pass a block that accepts the name or the full argument list for link_to_unless.

#### Examples

      <%= link_to_unless(@current_user.nil?, "Reply", { :action => "reply" }) %>
      # If the user is logged in...
      # => <a href="/controller/reply/">Reply</a>

      <%=
         link_to_unless(@current_user.nil?, "Reply", { :action => "reply" }) do |name|
           link_to(name, { :controller => "accounts", :action => "signup" })
         end
      %>
      # If the user is logged in...
      # => <a href="/controller/reply/">Reply</a>
      # If not...
      # => <a href="/accounts/signup">Reply</a>

link_to_unless_current(name, options = {}, html_options = {}, &block)

Creates a link tag of the given `name` using a URL created by the set of `options` unless the current request URI is the same as the links, in which case only the name is returned (or the given block is yielded, if one exists). You can give link_to_unless_current a block which will specialize the default behavior (e.g., show a "Start Here" link rather than the link‘s text).

#### Examples

Let‘s say you have a navigation menu…

      <ul id="navbar">
        <li><%= link_to_unless_current("Home", { :action => "index" }) %></li>
        <li><%= link_to_unless_current("About Us", { :action => "about" }) %></li>
      </ul>

If in the "about" action, it will render…

      <ul id="navbar">
        <li><a href="/controller/index">Home</a></li>
        <li>About Us</li>
      </ul>

…but if in the "index" action, it will render:

      <ul id="navbar">
        <li>Home</li>
        <li><a href="/controller/about">About Us</a></li>
      </ul>

The implicit block given to link_to_unless_current is evaluated if the current action is the action given. So, if we had a comments page and wanted to render a "Go Back" link instead of a link to the comments page, we could do something like this…

       <%=
           link_to_unless_current("Comment", { :controller => 'comments', :action => 'new}) do
              link_to("Go back", { :controller => 'posts', :action => 'index' })
           end
        %>

mail_to(email_address, name = nil, html_options = {})

Creates a mailto link tag to the specified `email_address`, which is also used as the name of the link unless `name` is specified. Additional HTML attributes for the link can be passed in `html_options`.

mail_to has several methods for hindering email harvesters and customizing the email itself by passing special keys to `html_options`.

#### Options

- `:encode` - This key will accept the strings "javascript" or "hex". Passing "javascript" will dynamically create and encode the mailto: link then eval it into the DOM of the page. This method will not show the link on the page if the user has JavaScript disabled. Passing "hex" will hex encode the `email_address` before outputting the mailto: link.
- `:replace_at` - When the link `name` isn‘t provided, the `email_address` is used for the link label. You can use this option to obfuscate the `email_address` by substituting the @ sign with the string given as the value.
- `:replace_dot` - When the link `name` isn‘t provided, the `email_address` is used for the link label. You can use this option to obfuscate the `email_address` by substituting the . in the email with the string given as the value.
- `:subject` - Preset the subject line of the email.
- `:body` - Preset the body of the email.
- `:cc` - Carbon Copy addition recipients on the email.
- `:bcc` - Blind Carbon Copy additional recipients on the email.

#### Examples

      mail_to "me@domain.com"
      # => <a href="mailto:me@domain.com">me@domain.com</a>

      mail_to "me@domain.com", "My email", :encode => "javascript"
      # => <script type="text/javascript">eval(decodeURIComponent('%64%6f%63...%27%29%3b'))</script>

      mail_to "me@domain.com", "My email", :encode => "hex"
      # => <a href="mailto:%6d%65@%64%6f%6d%61%69%6e.%63%6f%6d">My email</a>

      mail_to "me@domain.com", nil, :replace_at => "_at_", :replace_dot => "_dot_", :class => "email"
      # => <a href="mailto:me@domain.com" class="email">me_at_domain_dot_com</a>

      mail_to "me@domain.com", "My email", :cc => "ccaddress@domain.com",
               :subject => "This is an example email"
      # => <a href="mailto:me@domain.com?cc=ccaddress@domain.com&subject=This%20is%20an%20example%20email">My email</a>

url_for(options = {})

Returns the URL for the set of `options` provided. This takes the same options as `url_for` in Action Controller (see the documentation for ActionController::Base#url_for). Note that by default `:only_path` is `true` so you‘ll get the relative /controller/action instead of the fully qualified URL like example.com/controller/action.

When called from a view, url_for returns an HTML escaped url. If you need an unescaped url, pass `:escape => false` in the `options`.

#### Options

- `:anchor` - Specifies the anchor name to be appended to the path.
- `:only_path` - If true, returns the relative URL (omitting the protocol, host name, and port) (`true` by default unless `:host` is specified).
- `:trailing_slash` - If true, adds a trailing slash, as in "/archive/2005/". Note that this is currently not recommended since it breaks caching.
- `:host` - Overrides the default (current) host if provided.
- `:protocol` - Overrides the default (current) protocol if provided.
- `:user` - Inline HTTP authentication (only plucked out if `:password` is also present).
- `:password` - Inline HTTP authentication (only plucked out if `:user` is also present).
- `:escape` - Determines whether the returned URL will be HTML escaped or not (`true` by default).

#### Relying on named routes

If you instead of a hash pass a record (like an Active Record or Active Resource) as the options parameter, you‘ll trigger the named route for that record. The lookup will happen on the name of the class. So passing a Workshop object will attempt to use the workshop_path route. If you have a nested route, such as admin_workshop_path you‘ll have to call that explicitly (it‘s impossible for url_for to guess that route).

#### Examples

      <%= url_for(:action => 'index') %>
      # => /blog/

      <%= url_for(:action => 'find', :controller => 'books') %>
      # => /books/find

      <%= url_for(:action => 'login', :controller => 'members', :only_path => false, :protocol => 'https') %>
      # => https://www.railsapplication.com/members/login/

      <%= url_for(:action => 'play', :anchor => 'player') %>
      # => /messages/play/#player

      <%= url_for(:action => 'checkout', :anchor => 'tax&ship') %>
      # => /testing/jump/#tax&amp;ship

      <%= url_for(:action => 'checkout', :anchor => 'tax&ship', :escape => false) %>
      # => /testing/jump/#tax&ship

      <%= url_for(Workshop.new) %>
      # relies on Workshop answering a new_record? call (and in this case returning true)
      # => /workshops

      <%= url_for(@workshop) %>
      # calls @workshop.to_s
      # => /workshops/5

      <%= url_for("http://www.example.com") %>
      # => http://www.example.com

      <%= url_for(:back) %>
      # if request.env["HTTP_REFERER"] is set to "http://www.example.com"
      # => http://www.example.com

      <%= url_for(:back) %>
      # if request.env["HTTP_REFERER"] is not set or is blank
      # => javascript:history.back()

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