Active Support Parameter Filter

ParameterFilter replaces values in a Hash-like object if their keys match one of the specified filters.

Matching based on nested keys is possible by using dot notation, e.g. "credit_card.number".

If a proc is given as a filter, each key and value of the Hash-like and of any nested Hashes will be passed to it. The value or key can then be mutated as desired using methods such as String#replace.

# Replaces values with "[FILTERED]" for keys that match /password/i.
ActiveSupport::ParameterFilter.new([:password])

# Replaces values with "[FILTERED]" for keys that match /foo|bar/i.
ActiveSupport::ParameterFilter.new([:foo, "bar"])

# Replaces values for the exact key "pin" and for keys that begin with
# "pin_". Does not match keys that otherwise include "pin" as a
# substring, such as "shipping_id".
ActiveSupport::ParameterFilter.new([/\Apin\z/, /\Apin_/])

# Replaces the value for :code in `{ credit_card: { code: "xxxx" } }`.
# Does not change `{ file: { code: "xxxx" } }`.
ActiveSupport::ParameterFilter.new(["credit_card.code"])

# Reverses values for keys that match /secret/i.
ActiveSupport::ParameterFilter.new([-> (k, v) do
  v.reverse! if /secret/i.match?(k)
end])

Methods

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.

Options

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

📝 Source code 
# File activesupport/lib/active_support/parameter_filter.rb, line 77
    def initialize(filters = [], mask: FILTERED)
      @mask = mask
      compile_filters!(filters)
    end
🔎 See on GitHub

precompile_filters(filters)

Precompiles an array of filters that otherwise would be passed directly to initialize. Depending on the quantity and types of filters, precompilation can improve filtering performance, especially in the case where the ParameterFilter instance itself cannot be retained (but the precompiled filters can be retained).

filters = [/foo/, :bar, "nested.baz", /nested\.qux/]

precompiled = ActiveSupport::ParameterFilter.precompile_filters(filters)
# => [/(?-mix:foo)|(?i:bar)/, /(?i:nested\.baz)|(?-mix:nested\.qux)/]

ActiveSupport::ParameterFilter.new(precompiled)
📝 Source code 
# File activesupport/lib/active_support/parameter_filter.rb, line 55
    def self.precompile_filters(filters)
      filters, patterns = filters.partition { |filter| filter.is_a?(Proc) }

      patterns.map! do |pattern|
        pattern.is_a?(Regexp) ? pattern : "(?i:#{Regexp.escape pattern.to_s})"
      end

      deep_patterns = patterns.extract! { |pattern| pattern.to_s.include?("\\.") }

      filters << Regexp.new(patterns.join("|")) if patterns.any?
      filters << Regexp.new(deep_patterns.join("|")) if deep_patterns.any?

      filters
    end
🔎 See on GitHub

Instance Public methods

filter(params)

Mask value of params if key matches one of filters.

📝 Source code 
# File activesupport/lib/active_support/parameter_filter.rb, line 83
    def filter(params)
      @no_filters ? params.dup : call(params)
    end
🔎 See on GitHub

filter_param(key, value)

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

📝 Source code 
# File activesupport/lib/active_support/parameter_filter.rb, line 88
    def filter_param(key, value)
      @no_filters ? value : value_for_key(key, value)
    end
🔎 See on GitHub