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Provides access to the request's HTTP headers from the environment.

env     = { "CONTENT_TYPE" => "text/plain", "HTTP_USER_AGENT" => "curl/7.43.0" }
headers = ActionDispatch::Http::Headers.from_hash(env)
headers["Content-Type"] # => "text/plain"
headers["User-Agent"] # => "curl/7.43.0"

Also note that when headers are mapped to CGI-like variables by the Rack server, both dashes and underscores are converted to underscores. This ambiguity cannot be resolved at this stage anymore. Both underscores and dashes have to be interpreted as if they were originally sent as dashes.

# GET / HTTP/1.1
# ...
# User-Agent: curl/7.43.0
# X_Custom_Header: token

headers["X_Custom_Header"] # => nil
headers["X-Custom-Header"] # => "token"
Methods
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Included Modules
Constants
CGI_VARIABLES = Set.new(%W[ AUTH_TYPE CONTENT_LENGTH CONTENT_TYPE GATEWAY_INTERFACE HTTPS PATH_INFO PATH_TRANSLATED QUERY_STRING REMOTE_ADDR REMOTE_HOST REMOTE_IDENT REMOTE_USER REQUEST_METHOD SCRIPT_NAME SERVER_NAME SERVER_PORT SERVER_PROTOCOL SERVER_SOFTWARE ]).freeze
 
HTTP_HEADER = /\A[A-Za-z0-9-]+\z/
 
DEFAULT = Object.new # :nodoc:
 
Class Public methods
from_hash(hash)
# File actionpack/lib/action_dispatch/http/headers.rb, line 48
def self.from_hash(hash)
  new ActionDispatch::Request.new hash
end
Instance Public methods
[](key)

Returns the value for the given key mapped to @env.

# File actionpack/lib/action_dispatch/http/headers.rb, line 57
def [](key)
  @req.get_header env_name(key)
end
[]=(key, value)

Sets the given value for the key mapped to @env.

# File actionpack/lib/action_dispatch/http/headers.rb, line 62
def []=(key, value)
  @req.set_header env_name(key), value
end
add(key, value)

Add a value to a multivalued header like Vary or Accept-Encoding.

# File actionpack/lib/action_dispatch/http/headers.rb, line 67
def add(key, value)
  @req.add_header env_name(key), value
end
each(&block)
# File actionpack/lib/action_dispatch/http/headers.rb, line 93
def each(&block)
  @req.each_header(&block)
end
env()
# File actionpack/lib/action_dispatch/http/headers.rb, line 114
def env; @req.env.dup; end
fetch(key, default = DEFAULT)

Returns the value for the given key mapped to @env.

If the key is not found and an optional code block is not provided, raises a KeyError exception.

If the code block is provided, then it will be run and its result returned.

# File actionpack/lib/action_dispatch/http/headers.rb, line 85
def fetch(key, default = DEFAULT)
  @req.fetch_header(env_name(key)) do
    return default unless default == DEFAULT
    return yield if block_given?
    raise NameError, key
  end
end
include?(key)
Alias for: key?
key?(key)
Also aliased as: include?
# File actionpack/lib/action_dispatch/http/headers.rb, line 71
def key?(key)
  @req.has_header? env_name(key)
end
merge(headers_or_env)

Returns a new Http::Headers instance containing the contents of headers_or_env and the original instance.

# File actionpack/lib/action_dispatch/http/headers.rb, line 99
def merge(headers_or_env)
  headers = @req.dup.headers
  headers.merge!(headers_or_env)
  headers
end
merge!(headers_or_env)

Adds the contents of headers_or_env to original instance entries; duplicate keys are overwritten with the values from headers_or_env.

# File actionpack/lib/action_dispatch/http/headers.rb, line 108
def merge!(headers_or_env)
  headers_or_env.each do |key, value|
    @req.set_header env_name(key), value
  end
end