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module ActionDispatch::Http::Cache::Response

Constants

DATE
DEFAULT_CACHE_CONTROL
LAST_MODIFIED
MUST_REVALIDATE
NO_CACHE
NO_STORE
PRIVATE
PUBLIC
SPECIAL_KEYS

Attributes

cache_control[R]

Public Instance Methods

# 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) Show source

# File actionpack/lib/action_dispatch/http/cache.rb, line 78
def date=(utc_time)
  set_header DATE, utc_time.httpdate
end

date?() Show source

# File actionpack/lib/action_dispatch/http/cache.rb, line 74
def date?
  has_header? DATE
end

etag=(weak_validators) Show source

# File actionpack/lib/action_dispatch/http/cache.rb, line 101
def etag=(weak_validators)
  self.weak_etag = weak_validators
end

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.

etag?() Show source

# File actionpack/lib/action_dispatch/http/cache.rb, line 113
def etag?; etag; end

last_modified() Show source

# 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) Show source

# 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?() Show source

# File actionpack/lib/action_dispatch/http/cache.rb, line 60
def last_modified?
  has_header? LAST_MODIFIED
end

strong_etag=(strong_validators) Show source

# 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?() Show source

# File actionpack/lib/action_dispatch/http/cache.rb, line 121
def strong_etag?
  etag? && !weak_etag?
end

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

weak_etag=(weak_validators) Show source

# 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?() Show source

# File actionpack/lib/action_dispatch/http/cache.rb, line 116
def weak_etag?
  etag? && etag.start_with?('W/"')
end

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