Module: ActionController::Caching::Fragments

Defined in:
lib/action_controller/caching/fragments.rb

Overview

Fragment caching is used for caching various blocks within templates without caching the entire action as a whole. This is useful when certain elements of an action change frequently or depend on complicated state while other parts rarely change or can be shared amongst multiple parties. The caching is doing using the cache helper available in the Action View. A template with caching might look something like:

<b>Hello <%= @name %></b>
<% cache do %>
  All the topics in the system:
  <%= render :partial => "topic", :collection => Topic.find(:all) %>
<% end %>

This cache will bind to the name of the action that called it, so if this code was part of the view for the topics/list action, you would be able to invalidate it using expire_fragment(:controller => "topics", :action => "list").

This default behavior is of limited use if you need to cache multiple fragments per action or if the action itself is cached using caches_action, so we also have the option to qualify the name of the cached fragment with something like:

<% cache(:action => "list", :action_suffix => "all_topics") do %>

That would result in a name such as “/topics/list/all_topics”, avoiding conflicts with the action cache and with any fragments that use a different suffix. Note that the URL doesn’t have to really exist or be callable - the url_for system is just used to generate unique cache names that we can refer to when we need to expire the cache.

The expiration call for this example is:

expire_fragment(:controller => "topics", :action => "list", :action_suffix => "all_topics")

Class Method Summary collapse

Instance Method Summary collapse

Class Method Details

.included(base) ⇒ Object

:nodoc:



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# File 'lib/action_controller/caching/fragments.rb', line 29

def self.included(base) #:nodoc:
  base.class_eval do
    class << self
      def fragment_cache_store=(store_option) #:nodoc:
        ActiveSupport::Deprecation.warn('The fragment_cache_store= method is now use cache_store=')
        self.cache_store = store_option
      end
    
      def fragment_cache_store #:nodoc:
        ActiveSupport::Deprecation.warn('The fragment_cache_store method is now use cache_store')
        cache_store
      end
    end

    def fragment_cache_store=(store_option) #:nodoc:
      ActiveSupport::Deprecation.warn('The fragment_cache_store= method is now use cache_store=')
      self.cache_store = store_option
    end
  
    def fragment_cache_store #:nodoc:
      ActiveSupport::Deprecation.warn('The fragment_cache_store method is now use cache_store')
      cache_store
    end
  end
end

Instance Method Details

#expire_fragment(key, options = nil) ⇒ Object

Name can take one of three forms:

  • String: This would normally take the form of a path like “pages/45/notes”

  • Hash: Is treated as an implicit call to url_for, like { :controller => “pages”, :action => “notes”, :id => 45 }

  • Regexp: Will destroy all the matched fragments, example:

    %r{pages/\d*/notes}

    Ensure you do not specify start and finish in the regex (^$) because the actual filename matched looks like ./cache/filename/path.cache Regexp expiration is only supported on caches that can iterate over all keys (unlike memcached).



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# File 'lib/action_controller/caching/fragments.rb', line 121

def expire_fragment(key, options = nil)
  return unless cache_configured?

  key = key.is_a?(Regexp) ? key : fragment_cache_key(key)

  if key.is_a?(Regexp)
    self.class.benchmark "Expired fragments matching: #{key.source}" do
      cache_store.delete_matched(key, options)
    end
  else
    self.class.benchmark "Expired fragment: #{key}" do
      cache_store.delete(key, options)
    end
  end
end

#fragment_cache_key(key) ⇒ Object

Given a key (as described in expire_fragment), returns a key suitable for use in reading, writing, or expiring a cached fragment. If the key is a hash, the generated key is the return value of url_for on that hash (without the protocol). All keys are prefixed with “views/” and uses ActiveSupport::Cache.expand_cache_key for the expansion.



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# File 'lib/action_controller/caching/fragments.rb', line 59

def fragment_cache_key(key)
  ActiveSupport::Cache.expand_cache_key(key.is_a?(Hash) ? url_for(key).split("://").last : key, :views)
end

#fragment_exist?(key, options = nil) ⇒ Boolean

Check if a cached fragment from the location signified by key exists (see expire_fragment for acceptable formats)

Returns:

  • (Boolean) 


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# File 'lib/action_controller/caching/fragments.rb', line 102

def fragment_exist?(key, options = nil)
  return unless cache_configured?

  key = fragment_cache_key(key)

  self.class.benchmark "Cached fragment exists?: #{key}" do
    cache_store.exist?(key, options)
  end
end

#fragment_for(block, name = {}, options = nil) ⇒ Object

:nodoc:



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# File 'lib/action_controller/caching/fragments.rb', line 63

def fragment_for(block, name = {}, options = nil) #:nodoc:
  unless perform_caching then block.call; return end

  buffer = yield

  if cache = read_fragment(name, options)
    buffer.concat(cache)
  else
    pos = buffer.length
    block.call
    write_fragment(name, buffer[pos..-1], options)
  end
end

#read_fragment(key, options = nil) ⇒ Object

Reads a cached fragment from the location signified by key (see expire_fragment for acceptable formats)



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# File 'lib/action_controller/caching/fragments.rb', line 91

def read_fragment(key, options = nil)
  return unless cache_configured?

  key = fragment_cache_key(key)

  self.class.benchmark "Cached fragment hit: #{key}" do
    cache_store.read(key, options)
  end
end

#write_fragment(key, content, options = nil) ⇒ Object

Writes content to the location signified by key (see expire_fragment for acceptable formats)



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# File 'lib/action_controller/caching/fragments.rb', line 78

def write_fragment(key, content, options = nil)
  return unless cache_configured?

  key = fragment_cache_key(key)

  self.class.benchmark "Cached fragment miss: #{key}" do
    cache_store.write(key, content, options)
  end

  content
end