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

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

Instance Attribute Summary collapse

Instance Method Summary collapse

Instance Attribute Details

#cache_controlObject (readonly)

Returns the value of attribute cache_control


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

def cache_control
  @cache_control
end

Instance Method Details

#dateObject


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# File 'actionpack/lib/action_dispatch/http/cache.rb', line 68

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

#date=(utc_time) ⇒ Object


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# File 'actionpack/lib/action_dispatch/http/cache.rb', line 78

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

#date?Boolean

Returns:

  • (Boolean)

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# File 'actionpack/lib/action_dispatch/http/cache.rb', line 74

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 'actionpack/lib/action_dispatch/http/cache.rb', line 101

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

#etag?Boolean

Returns:

  • (Boolean)

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# File 'actionpack/lib/action_dispatch/http/cache.rb', line 113

def etag?; etag; end

#last_modifiedObject


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# File 'actionpack/lib/action_dispatch/http/cache.rb', line 54

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

#last_modified=(utc_time) ⇒ Object


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# File 'actionpack/lib/action_dispatch/http/cache.rb', line 64

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

#last_modified?Boolean

Returns:

  • (Boolean)

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# File 'actionpack/lib/action_dispatch/http/cache.rb', line 60

def last_modified?
  has_header? LAST_MODIFIED
end

#strong_etag=(strong_validators) ⇒ Object


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# File 'actionpack/lib/action_dispatch/http/cache.rb', line 109

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 'actionpack/lib/action_dispatch/http/cache.rb', line 121

def strong_etag?
  etag? && !weak_etag?
end

#weak_etag=(weak_validators) ⇒ Object


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# File 'actionpack/lib/action_dispatch/http/cache.rb', line 105

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 'actionpack/lib/action_dispatch/http/cache.rb', line 116

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