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ParameterFilter allows you to specify keys for sensitive data from hash-like object and replace corresponding value. Filtering only certain sub-keys from a hash is possible by using the dot notation: 'credit_card.number'. If a proc is given, each key and value of a hash and all sub-hashes are passed to it, where the value or the key can be replaced using String#replace or similar methods.[:password])
=> replaces the value to all keys matching /password/i with "[FILTERED]"[:foo, "bar"])
=> replaces the value to all keys matching /foo|bar/i with "[FILTERED]"[/\Apin\z/i, /\Apin_/i])
=> replaces the value for the exact (case-insensitive) key 'pin' and all
(case-insensitive) keys beginning with 'pin_', with "[FILTERED]".
Does not match keys with 'pin' as a substring, such as 'shipping_id'.["credit_card.code"])
=> replaces { credit_card: {code: "xxxx"} } with "[FILTERED]", does not
change { file: { code: "xxxx"} }[-> (k, v) do
  v.reverse! if /secret/i.match?(k)
=> reverses the value to all keys matching /secret/i

Class Public methods

new(filters = [], mask: FILTERED)

Create instance with given filters. Supported type of filters are String, Regexp, and Proc. Other types of filters are treated as String using to_s. For Proc filters, key, value, and optional original hash is passed to block arguments.


  • :mask - A replaced object when filtered. Defaults to "[FILTERED]".

# File activesupport/lib/active_support/parameter_filter.rb, line 42
def initialize(filters = [], mask: FILTERED)
  @filters = filters
  @mask = mask

Instance Public methods


Mask value of params if key matches one of filters.

# File activesupport/lib/active_support/parameter_filter.rb, line 48
def filter(params)

filter_param(key, value)

Returns filtered value for given key. For Proc filters, third block argument is not populated.

# File activesupport/lib/active_support/parameter_filter.rb, line 53
def filter_param(key, value)
  @filters.empty? ? value : compiled_filter.value_for_key(key, value)