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Module: ActionDispatch::Http::Cache::Response

Constant Summary

Instance Attribute Summary

Instance Method Summary

Instance Attribute Details

#cache_control (readonly)

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# File 'actionpack/lib/action_dispatch/http/cache.rb', line 179



attr_reader :cache_control


  








  

    #date   (rw)
  

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# File 'actionpack/lib/action_dispatch/http/cache.rb', line 195



def date
  if date_header = get_header(DATE)
    Time.httpdate(date_header)
  end
end


  








  

    #date=(utc_time)   (rw)
  

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# File 'actionpack/lib/action_dispatch/http/cache.rb', line 205



def date=(utc_time)
  set_header DATE, utc_time.httpdate
end


  








  

    #date?  ⇒ Boolean  (rw)
  

  [ GitHub ]


  

  


# File 'actionpack/lib/action_dispatch/http/cache.rb', line 201



def date?
  has_header? DATE
end


  








  

    #etag=(weak_validators)   (rw)
  



  

    
This method sets a weak ETag validator on the response so browsers and proxies
may cache the response, keyed on the ETag. On subsequent requests, the
If-None-Match header is set to the cached ETag. If it matches the current
ETag, we can return a 304 Not Modified response with no body, letting the
browser or proxy know that their cache is current. Big savings in request time
and network bandwidth.


Weak ETags are considered to be semantically equivalent but not byte-for-byte
identical. This is perfect for browser caching of HTML pages where we don't
care about exact equality, just what the user is viewing.


Strong ETags are considered byte-for-byte identical. They allow a browser or
proxy cache to support ::Range requests, useful for paging through a PDF file
or scrubbing through a video. Some CDNs only support strong ETags and will
ignore weak ETags entirely.


Weak ETags are what we almost always need, so they're the default. Check out
#strong_etag= to provide a strong ETag validator.

  



  [ GitHub ]


  

  


# File 'actionpack/lib/action_dispatch/http/cache.rb', line 227



def etag=(weak_validators)
  self.weak_etag = weak_validators
end


  








  

    #etag?  ⇒ Boolean  (rw)
  

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# File 'actionpack/lib/action_dispatch/http/cache.rb', line 239



def etag?; etag; end


  








  

    #last_modified   (rw)
  

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# File 'actionpack/lib/action_dispatch/http/cache.rb', line 181



def last_modified
  if last = get_header(LAST_MODIFIED)
    Time.httpdate(last)
  end
end


  








  

    #last_modified=(utc_time)   (rw)
  

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# File 'actionpack/lib/action_dispatch/http/cache.rb', line 191



def last_modified=(utc_time)
  set_header LAST_MODIFIED, utc_time.httpdate
end


  








  

    #last_modified?  ⇒ Boolean  (rw)
  

  [ GitHub ]


  

  


# File 'actionpack/lib/action_dispatch/http/cache.rb', line 187



def last_modified?
  has_header? LAST_MODIFIED
end


  








  

    #strong_etag=(strong_validators)   (rw)
  

  [ GitHub ]


  

  


# File 'actionpack/lib/action_dispatch/http/cache.rb', line 235



def strong_etag=(strong_validators)
  set_header "ETag", generate_strong_etag(strong_validators)
end


  








  

    #strong_etag?  ⇒ Boolean  (rw)
  



  

    
True if an ETag is set, and it isn't a weak validator (not preceded with
W/).

  





  


  [ GitHub ]


  

  


# File 'actionpack/lib/action_dispatch/http/cache.rb', line 248



def strong_etag?
  etag? && !weak_etag?
end


  








  

    #weak_etag=(weak_validators)   (rw)
  

  [ GitHub ]


  

  


# File 'actionpack/lib/action_dispatch/http/cache.rb', line 231



def weak_etag=(weak_validators)
  set_header "ETag", generate_weak_etag(weak_validators)
end


  








  

    #weak_etag?  ⇒ Boolean  (rw)
  



  

    
True if an ETag is set, and it's a weak validator (preceded with W/).

  





  


  [ GitHub ]


  

  


# File 'actionpack/lib/action_dispatch/http/cache.rb', line 242



def weak_etag?
  etag? && etag.start_with?('W/"')
end


  







Instance Method Details



  

    #cache_control_headers   (private)
  

  [ GitHub ]


  

  


# File 'actionpack/lib/action_dispatch/http/cache.rb', line 271



def cache_control_headers
  cache_control = {}

  cache_control_segments&.each do |segment|
    directive, argument = segment.split("=", 2)

    if SPECIAL_KEYS.include? directive
      directive.tr!("-", "_")
      cache_control[directive.to_sym] = argument || true
    else
      cache_control[:extras] ||= []
      cache_control[:extras] << segment
    end
  end

  cache_control
end


  








  

    #cache_control_segments   (private)
  

  [ GitHub ]


  

  


# File 'actionpack/lib/action_dispatch/http/cache.rb', line 265



def cache_control_segments
  if cache_control = _cache_control
    cache_control.delete(" ").split(",")
  end
end


  








  

    #generate_strong_etag(validators)   (private)
  

  [ GitHub ]


  

  


# File 'actionpack/lib/action_dispatch/http/cache.rb', line 261



def generate_strong_etag(validators)
  %("#{ActiveSupport::Digest.hexdigest(ActiveSupport::Cache.expand_cache_key(validators))}")
end


  








  

    #generate_weak_etag(validators)   (private)
  

  [ GitHub ]


  

  


# File 'actionpack/lib/action_dispatch/http/cache.rb', line 257



def generate_weak_etag(validators)
  "W/#{generate_strong_etag(validators)}"
end


  








  

    #handle_conditional_get!   (private)
  

  [ GitHub ]


  

  


# File 'actionpack/lib/action_dispatch/http/cache.rb', line 302



def handle_conditional_get!
  # Normally default cache control setting is handled by ETag middleware. But, if
  # an etag is already set, the middleware defaults to `no-cache` unless a default
  # `Cache-Control` value is previously set. So, set a default one here.
  if (etag? || last_modified?) && !self._cache_control
    self._cache_control = DEFAULT_CACHE_CONTROL
  end
end


  








  

    #merge_and_normalize_cache_control!(cache_control)   (private)
  

  [ GitHub ]


  

  


# File 'actionpack/lib/action_dispatch/http/cache.rb', line 311



def merge_and_normalize_cache_control!(cache_control)
  control = cache_control_headers

  return if control.empty? && cache_control.empty?  # Let middleware handle default behavior

  if cache_control.any?
    # Any caching directive coming from a controller overrides no-cache/no-store in
    # the default Cache-Control header.
    control.delete(:no_cache)
    control.delete(:no_store)

    if extras = control.delete(:extras)
      cache_control[:extras] ||= []
      cache_control[:extras] += extras
      cache_control[:extras].uniq!
    end

    control.merge! cache_control
  end

  options = []

  if control[:no_store]
    options << PRIVATE if control[:private]
    options << MUST_UNDERSTAND if control[:must_understand]
    options << NO_STORE
  elsif control[:no_cache]
    options << PUBLIC if control[:public]
    options << NO_CACHE
    options.concat(control[:extras]) if control[:extras]
  else
    extras = control[:extras]
    max_age = control[:max_age]
    stale_while_revalidate = control[:stale_while_revalidate]
    stale_if_error = control[:stale_if_error]

    options << "max-age=#{max_age.to_i}" if max_age
    options << (control[:public] ? PUBLIC : PRIVATE)
    options << MUST_REVALIDATE if control[:must_revalidate]
    options << "stale-while-revalidate=#{stale_while_revalidate.to_i}" if stale_while_revalidate
    options << "stale-if-error=#{stale_if_error.to_i}" if stale_if_error
    options << IMMUTABLE if control[:immutable]
    options.concat(extras) if extras
  end

  self._cache_control = options.join(", ")
end


  








  

    #prepare_cache_control!   (private)
  

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# File 'actionpack/lib/action_dispatch/http/cache.rb', line 289



def prepare_cache_control!
  @cache_control = cache_control_headers
end