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Module: AbstractController::Caching::Fragments

Overview

Fragment caching is used for caching various blocks within views 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 done using the #cache helper available in the Action View. See ::ActionView::Helpers::CacheHelper for more information.

While it’s strongly recommended that you use key-based cache expiration (see links in CacheHelper for more information), it is also possible to manually expire caches. For example:

expire_fragment('name_of_cache')

Class Method Summary

::ActiveSupport::Concern - Extended

class_methods

Define class methods from given block.
included

Evaluate given block in context of base class, so that you can write class macros here.
prepended

Evaluate given block in context of base class, so that you can write class macros here.
append_features, prepend_features

Instance Method Summary

DSL Calls

included

[ GitHub ] 


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# File 'actionpack/lib/abstract_controller/caching/fragments.rb', line 24

included do
  if respond_to?(:class_attribute)
    class_attribute :fragment_cache_keys
  else
    mattr_writer :fragment_cache_keys
  end

  self.fragment_cache_keys = []

  if respond_to?(:helper_method)
    helper_method :combined_fragment_cache_key
  end
end

Instance Method Details

#combined_fragment_cache_key(key)

Given a key (as described in #expire_fragment), returns a key array suitable for use in reading, writing, or expiring a cached fragment. All keys begin with :views, followed by "RAILS_CACHE_ID" or "RAILS_APP_VERSION" if set, followed by any controller-wide key prefix values, ending with the specified key value.

[ GitHub ] 

  


# File 'actionpack/lib/abstract_controller/caching/fragments.rb', line 68



def combined_fragment_cache_key(key)
  head = self.class.fragment_cache_keys.map { |k| instance_exec(&k) }
  tail = key.is_a?(Hash) ? url_for(key).split("://").last : key

  cache_key = [:views, ENV["RAILS_CACHE_ID"] || ENV["RAILS_APP_VERSION"], head, tail]
  cache_key.flatten!(1)
  cache_key.compact!
  cache_key
end


  








  

    #expire_fragment(key, options = nil)  
  



  

    

Removes fragments from the cache.



key can take one of three forms:


  • 

    ::String - This would normally take the form of a path, like pages/45/notes.
    

  • 

    ::Hash - Treated as an implicit call to url_for, like ‘{ controller: ’pages’, action: ‘notes’, id: 45}‘
    

  • 

    ::Regexp - Will remove any fragment that matches, so %r{pages/\d*/notes} might remove all notes. Make sure you don’t use anchors in the regex (‘^` or $) because the actual filename matched looks like ./cache/filename/path.cache. Note: Regexp expiration is only supported on caches that can iterate over all keys (unlike memcached).
    




options is passed through to the cache store’s delete method (or delete_matched, for ::Regexp keys).


  



  [ GitHub ]


  

  


# File 'actionpack/lib/abstract_controller/caching/fragments.rb', line 131



def expire_fragment(key, options = nil)
  return unless cache_configured?
  key = combined_fragment_cache_key(key) unless key.is_a?(Regexp)

  instrument_fragment_cache :expire_fragment, key do
    if key.is_a?(Regexp)
      cache_store.delete_matched(key, options)
    else
      cache_store.delete(key, options)
    end
  end
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).


  





  


  [ GitHub ]


  

  


# File 'actionpack/lib/abstract_controller/caching/fragments.rb', line 105



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

  instrument_fragment_cache :exist_fragment?, key do
    cache_store.exist?(key, options)
  end
end


  








  

    #instrument_fragment_cache(name, key, &block)  
  

  

    This method is for internal use only.
  

  [ GitHub ]


  

  


# File 'actionpack/lib/abstract_controller/caching/fragments.rb', line 144



def instrument_fragment_cache(name, key, &block) # :nodoc:
  ActiveSupport::Notifications.instrument("#{name}.#{instrument_name}", instrument_payload(key), &block)
end


  








  

    #read_fragment(key, options = nil)  
  



  

    

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


  



  [ GitHub ]


  

  


# File 'actionpack/lib/abstract_controller/caching/fragments.rb', line 93



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

  key = combined_fragment_cache_key(key)
  instrument_fragment_cache :read_fragment, key do
    result = cache_store.read(key, options)
    result.respond_to?(:html_safe) ? result.html_safe : result
  end
end


  








  

    #write_fragment(key, content, options = nil)  
  



  

    

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


  



  [ GitHub ]


  

  


# File 'actionpack/lib/abstract_controller/caching/fragments.rb', line 80



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

  key = combined_fragment_cache_key(key)
  instrument_fragment_cache :write_fragment, key do
    content = content.to_str
    cache_store.write(key, content, options)
  end
  content
end