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


51
52
53
# File 'actionpack/lib/action_dispatch/http/cache.rb', line 51

def cache_control
  @cache_control
end

Instance Method Details

#dateObject


67
68
69
70
71
# File 'actionpack/lib/action_dispatch/http/cache.rb', line 67

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

#date=(utc_time) ⇒ Object


77
78
79
# File 'actionpack/lib/action_dispatch/http/cache.rb', line 77

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

#date?Boolean


73
74
75
# File 'actionpack/lib/action_dispatch/http/cache.rb', line 73

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.


100
101
102
# File 'actionpack/lib/action_dispatch/http/cache.rb', line 100

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

#etag?Boolean


112
# File 'actionpack/lib/action_dispatch/http/cache.rb', line 112

def etag?; etag; end

#last_modifiedObject


53
54
55
56
57
# File 'actionpack/lib/action_dispatch/http/cache.rb', line 53

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

#last_modified=(utc_time) ⇒ Object


63
64
65
# File 'actionpack/lib/action_dispatch/http/cache.rb', line 63

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

#last_modified?Boolean


59
60
61
# File 'actionpack/lib/action_dispatch/http/cache.rb', line 59

def last_modified?
  has_header? LAST_MODIFIED
end

#strong_etag=(strong_validators) ⇒ Object


108
109
110
# File 'actionpack/lib/action_dispatch/http/cache.rb', line 108

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/)


120
121
122
# File 'actionpack/lib/action_dispatch/http/cache.rb', line 120

def strong_etag?
  etag? && !weak_etag?
end

#weak_etag=(weak_validators) ⇒ Object


104
105
106
# File 'actionpack/lib/action_dispatch/http/cache.rb', line 104

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/)


115
116
117
# File 'actionpack/lib/action_dispatch/http/cache.rb', line 115

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