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<title>Module: ActionController::Helpers::ClassMethods</title>
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<tr class="top-aligned-row">
<td><strong>Module</strong></td>
<td class="class-name-in-header">ActionController::Helpers::ClassMethods</td>
</tr>
<tr class="top-aligned-row">
<td><strong>In:</strong></td>
<td>
<a href="../../../files/lib/action_controller/helpers_rb.html">
lib/action_controller/helpers.rb
</a>
<br />
</td>
</tr>
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<div id="description">
<p>
The Rails framework provides a large number of <a
href="ClassMethods.html#M000142">helpers</a> for working with
<tt>assets</tt>, <tt>dates</tt>, <tt>forms</tt>, <tt>numbers</tt> and
Active Record objects, to name a few. These <a
href="ClassMethods.html#M000142">helpers</a> are available to all templates
by default.
</p>
<p>
In addition to using the standard template <a
href="ClassMethods.html#M000142">helpers</a> provided in the Rails
framework, creating custom <a href="ClassMethods.html#M000142">helpers</a>
to extract complicated logic or reusable functionality is strongly
encouraged. By default, the controller will include a <a
href="ClassMethods.html#M000139">helper</a> whose name matches that of the
controller, e.g., <tt>MyController</tt> will automatically include
<tt>MyHelper</tt>.
</p>
<p>
Additional <a href="ClassMethods.html#M000142">helpers</a> can be specified
using the <tt><a href="ClassMethods.html#M000139">helper</a></tt> class
method in <tt><a href="../Base.html">ActionController::Base</a></tt> or any
controller which inherits from it.
</p>
<h4>Examples</h4>
<p>
The <tt>to_s</tt> method from the Time class can be wrapped in a <a
href="ClassMethods.html#M000139">helper</a> method to display a custom
message if the Time object is blank:
</p>
<pre>
module FormattedTimeHelper
def format_time(time, format=:long, blank_message="&nbsp;")
time.blank? ? blank_message : time.to_s(format)
end
end
</pre>
<p>
FormattedTimeHelper can now be included in a controller, using the <tt><a
href="ClassMethods.html#M000139">helper</a></tt> class method:
</p>
<pre>
class EventsController < ActionController::Base
helper FormattedTimeHelper
def index
@events = Event.find(:all)
end
end
</pre>
<p>
Then, in any view rendered by <tt>EventController</tt>, the
<tt>format_time</tt> method can be called:
</p>
<pre>
<% @events.each do |event| -%>
<p>
<% format_time(event.time, :short, "N/A") %> | <%= event.name %>
</p>
<% end -%>
</pre>
<p>
Finally, assuming we have two event instances, one which has a time and one
which does not, the output might look like this:
</p>
<pre>
23 Aug 11:30 | Carolina Railhawks Soccer Match
N/A | Carolina Railhaws Training Workshop
</pre>
</div>
</div>
<div id="method-list">
<h3 class="section-bar">Methods</h3>
<div class="name-list">
<a href="#M000139">helper</a>
<a href="#M000141">helper_attr</a>
<a href="#M000140">helper_method</a>
<a href="#M000142">helpers</a>
</div>
</div>
</div>
<!-- if includes -->
<div id="section">
<!-- if method_list -->
<div id="methods">
<h3 class="section-bar">Public Instance methods</h3>
<div id="method-M000139" class="method-detail">
<a name="M000139"></a>
<div class="method-heading">
<a href="ClassMethods.src/M000139.html" target="Code" class="method-signature"
onclick="popupCode('ClassMethods.src/M000139.html');return false;">
<span class="method-name">helper</span><span class="method-args">(*args, &block)</span>
</a>
</div>
<div class="method-description">
<p>
The <tt><a href="ClassMethods.html#M000139">helper</a></tt> class method
can take a series of <a href="ClassMethods.html#M000139">helper</a> module
names, a block, or both.
</p>
<ul>
<li><tt>*args</tt>: One or more modules, strings or symbols, or the special
symbol <tt>:all</tt>.
</li>
<li><tt>&block</tt>: A block defining <a
href="ClassMethods.html#M000139">helper</a> methods.
</li>
</ul>
<h4>Examples</h4>
<p>
When the argument is a string or symbol, the method will provide the
"_helper" suffix, require the file and include the module in the
template class. The second form illustrates how to include custom <a
href="ClassMethods.html#M000142">helpers</a> when working with namespaced
controllers, or other cases where the file containing the <a
href="ClassMethods.html#M000139">helper</a> definition is not in one of
Rails’ standard load paths:
</p>
<pre>
helper :foo # => requires 'foo_helper' and includes FooHelper
helper 'resources/foo' # => requires 'resources/foo_helper' and includes Resources::FooHelper
</pre>
<p>
When the argument is a module it will be included directly in the template
class.
</p>
<pre>
helper FooHelper # => includes FooHelper
</pre>
<p>
When the argument is the symbol <tt>:all</tt>, the controller will include
all <a href="ClassMethods.html#M000142">helpers</a> beneath
<tt>ActionController::Base.helpers_dir</tt> (defaults to
<tt>app/helpers/**/*.rb</tt> under RAILS_ROOT).
</p>
<pre>
helper :all
</pre>
<p>
Additionally, the <tt><a href="ClassMethods.html#M000139">helper</a></tt>
class method can receive and evaluate a block, making the methods defined
available to the template.
</p>
<pre>
# One line
helper { def hello() "Hello, world!" end }
# Multi-line
helper do
def foo(bar)
"#{bar} is the very best"
end
end
</pre>
<p>
Finally, all the above styles can be mixed together, and the <tt><a
href="ClassMethods.html#M000139">helper</a></tt> method can be invoked with
a mix of <tt>symbols</tt>, <tt>strings</tt>, <tt>modules</tt> and blocks.
</p>
<pre>
helper(:three, BlindHelper) { def mice() 'mice' end }
</pre>
</div>
</div>
<div id="method-M000141" class="method-detail">
<a name="M000141"></a>
<div class="method-heading">
<a href="ClassMethods.src/M000141.html" target="Code" class="method-signature"
onclick="popupCode('ClassMethods.src/M000141.html');return false;">
<span class="method-name">helper_attr</span><span class="method-args">(*attrs)</span>
</a>
</div>
<div class="method-description">
<p>
Declares <a href="ClassMethods.html#M000139">helper</a> accessors for
controller attributes. For example, the following adds new <tt>name</tt>
and <tt>name=</tt> instance methods to a controller and makes them
available to the view:
</p>
<pre>
helper_attr :name
attr_accessor :name
</pre>
</div>
</div>
<div id="method-M000140" class="method-detail">
<a name="M000140"></a>
<div class="method-heading">
<a href="ClassMethods.src/M000140.html" target="Code" class="method-signature"
onclick="popupCode('ClassMethods.src/M000140.html');return false;">
<span class="method-name">helper_method</span><span class="method-args">(*methods)</span>
</a>
</div>
<div class="method-description">
<p>
Declare a controller method as a <a
href="ClassMethods.html#M000139">helper</a>. For example, the following
makes the <tt>current_user</tt> controller method available to the view:
</p>
<pre>
class ApplicationController < ActionController::Base
helper_method :current_user, :logged_in?
def current_user
@current_user ||= User.find_by_id(session[:user])
end
def logged_in?
current_user != nil
end
end
</pre>
<p>
In a view:
</p>
<pre>
<% if logged_in? -%>Welcome, <%= current_user.name %><% end -%>
</pre>
</div>
</div>
<div id="method-M000142" class="method-detail">
<a name="M000142"></a>
<div class="method-heading">
<a href="ClassMethods.src/M000142.html" target="Code" class="method-signature"
onclick="popupCode('ClassMethods.src/M000142.html');return false;">
<span class="method-name">helpers</span><span class="method-args">()</span>
</a>
</div>
<div class="method-description">
<p>
Provides a proxy to access <a href="ClassMethods.html#M000142">helpers</a>
methods from outside the view.
</p>
</div>
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