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

Included in:
Response
Defined in:
lib/action_dispatch/http/cache.rb

Instance Attribute Summary collapse

Instance Method Summary collapse

Instance Attribute Details

#cache_control ⇒ Object (readonly)

Returns the value of attribute cache_control.



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# File 'lib/action_dispatch/http/cache.rb', line 50

def cache_control
  @cache_control
end

Instance Method Details

#date ⇒ Object 



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# File 'lib/action_dispatch/http/cache.rb', line 66

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

#date=(utc_time) ⇒ Object 



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# File 'lib/action_dispatch/http/cache.rb', line 76

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

#date? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/action_dispatch/http/cache.rb', line 72

def date?
  has_header? DATE
end

#etag=(weak_validators) ⇒ Object

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.



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# File 'lib/action_dispatch/http/cache.rb', line 99

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

#etag? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/action_dispatch/http/cache.rb', line 111

def etag?; etag; end

#last_modified ⇒ Object 



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# File 'lib/action_dispatch/http/cache.rb', line 52

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

#last_modified=(utc_time) ⇒ Object 



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# File 'lib/action_dispatch/http/cache.rb', line 62

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

#last_modified? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/action_dispatch/http/cache.rb', line 58

def last_modified?
  has_header? LAST_MODIFIED
end

#strong_etag=(strong_validators) ⇒ Object 



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# File 'lib/action_dispatch/http/cache.rb', line 107

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

#strong_etag? ⇒ Boolean

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

Returns:

  • (Boolean) 


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# File 'lib/action_dispatch/http/cache.rb', line 119

def strong_etag?
  etag? && !weak_etag?
end

#weak_etag=(weak_validators) ⇒ Object 



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# File 'lib/action_dispatch/http/cache.rb', line 103

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

#weak_etag? ⇒ Boolean

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

Returns:

  • (Boolean) 


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# File 'lib/action_dispatch/http/cache.rb', line 114

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