class ActionController::Parameters

Action Controller Parameters

Allows to choose which attributes should be whitelisted for mass updating and thus prevent accidentally exposing that which shouldn’t be exposed. Provides two methods for this purpose: require and permit. The former is used to mark parameters as required. The latter is used to set the parameter as permitted and limit which attributes should be allowed for mass updating.

params = ActionController::Parameters.new({
  person: {
    name: 'Francesco',
    age:  22,
    role: 'admin'
  }
})

permitted = params.require(:person).permit(:name, :age)
permitted            # => {"name"=>"Francesco", "age"=>22}
permitted.class      # => ActionController::Parameters
permitted.permitted? # => true

Person.first.update!(permitted)
# => #<Person id: 1, name: "Francesco", age: 22, role: "user">

It provides two options that controls the top-level behavior of new instances:

Examples:

params = ActionController::Parameters.new
params.permitted? # => false

ActionController::Parameters.permit_all_parameters = true

params = ActionController::Parameters.new
params.permitted? # => true

params = ActionController::Parameters.new(a: "123", b: "456")
params.permit(:c)
# => {}

ActionController::Parameters.action_on_unpermitted_parameters = :raise

params = ActionController::Parameters.new(a: "123", b: "456")
params.permit(:c)
# => ActionController::UnpermittedParameters: found unpermitted keys: a, b

ActionController::Parameters is inherited from ActiveSupport::HashWithIndifferentAccess, this means that you can fetch values using either :key or "key".

params = ActionController::Parameters.new(key: 'value')
params[:key]  # => "value"
params["key"] # => "value"

Constants

EMPTY_ARRAY
NEVER_UNPERMITTED_PARAMS

Never raise an UnpermittedParameters exception because of these params are present. They are added by Rails and it's of no concern.

PERMITTED_SCALAR_TYPES

This is a white list of permitted scalar types that includes the ones supported in XML and JSON requests.

This list is in particular used to filter ordinary requests, String goes as first element to quickly short-circuit the common case.

If you modify this collection please update the API of permit above.

Public Class Methods

new(attributes = nil) click to toggle source

Returns a new instance of ActionController::Parameters. Also, sets the permitted attribute to the default value of ActionController::Parameters.permit_all_parameters.

class Person < ActiveRecord::Base
end

params = ActionController::Parameters.new(name: 'Francesco')
params.permitted?  # => false
Person.new(params) # => ActiveModel::ForbiddenAttributesError

ActionController::Parameters.permit_all_parameters = true

params = ActionController::Parameters.new(name: 'Francesco')
params.permitted?  # => true
Person.new(params) # => #<Person id: nil, name: "Francesco">
Calls superclass method
# File lib/action_controller/metal/strong_parameters.rb, line 123
def initialize(attributes = nil)
  super(attributes)
  @permitted = self.class.permit_all_parameters
end

Public Instance Methods

[](key) click to toggle source

Returns a parameter for the given key. If not found, returns nil.

params = ActionController::Parameters.new(person: { name: 'Francesco' })
params[:person] # => {"name"=>"Francesco"}
params[:none]   # => nil
Calls superclass method
# File lib/action_controller/metal/strong_parameters.rb, line 270
def [](key)
  convert_hashes_to_parameters(key, super)
end
dup() click to toggle source

Returns an exact copy of the ActionController::Parameters instance. permitted state is kept on the duped object.

params = ActionController::Parameters.new(a: 1)
params.permit!
params.permitted?        # => true
copy_params = params.dup # => {"a"=>1}
copy_params.permitted?   # => true
Calls superclass method
# File lib/action_controller/metal/strong_parameters.rb, line 312
def dup
  super.tap do |duplicate|
    duplicate.instance_variable_set :@permitted, @permitted
  end
end
fetch(key, *args) click to toggle source

Returns a parameter for the given key. If the key can't be found, there are several options: With no other arguments, it will raise an ActionController::ParameterMissing error; if more arguments are given, then that will be returned; if a block is given, then that will be run and its result returned.

params = ActionController::Parameters.new(person: { name: 'Francesco' })
params.fetch(:person)               # => {"name"=>"Francesco"}
params.fetch(:none)                 # => ActionController::ParameterMissing: param not found: none
params.fetch(:none, 'Francesco')    # => "Francesco"
params.fetch(:none) { 'Francesco' } # => "Francesco"
Calls superclass method
# File lib/action_controller/metal/strong_parameters.rb, line 285
def fetch(key, *args)
  convert_hashes_to_parameters(key, super)
rescue KeyError
  raise ActionController::ParameterMissing.new(key)
end
permit(*filters) click to toggle source

Returns a new ActionController::Parameters instance that includes only the given filters and sets the permitted attribute for the object to true. This is useful for limiting which attributes should be allowed for mass updating.

params = ActionController::Parameters.new(user: { name: 'Francesco', age: 22, role: 'admin' })
permitted = params.require(:user).permit(:name, :age)
permitted.permitted?      # => true
permitted.has_key?(:name) # => true
permitted.has_key?(:age)  # => true
permitted.has_key?(:role) # => false

Only permitted scalars pass the filter. For example, given

params.permit(:name)

:name passes it is a key of params whose associated value is of type String, Symbol, NilClass, Numeric, TrueClass, FalseClass, Date, Time, DateTime, StringIO, IO, +ActionDispatch::Http::UploadedFile+ or +Rack::Test::UploadedFile+. Otherwise, the key :name is filtered out.

You may declare that the parameter should be an array of permitted scalars by mapping it to an empty array:

params.permit(tags: [])

You can also use permit on nested parameters, like:

params = ActionController::Parameters.new({
  person: {
    name: 'Francesco',
    age:  22,
    pets: [{
      name: 'Purplish',
      category: 'dogs'
    }]
  }
})

permitted = params.permit(person: [ :name, { pets: :name } ])
permitted.permitted?                    # => true
permitted[:person][:name]               # => "Francesco"
permitted[:person][:age]                # => nil
permitted[:person][:pets][0][:name]     # => "Purplish"
permitted[:person][:pets][0][:category] # => nil

Note that if you use permit in a key that points to a hash, it won't allow all the hash. You also need to specify which attributes inside the hash should be whitelisted.

params = ActionController::Parameters.new({
  person: {
    contact: {
      email: 'none@test.com',
      phone: '555-1234'
    }
  }
})

params.require(:person).permit(:contact)
# => {}

params.require(:person).permit(contact: :phone)
# => {"contact"=>{"phone"=>"555-1234"}}

params.require(:person).permit(contact: [ :email, :phone ])
# => {"contact"=>{"email"=>"none@test.com", "phone"=>"555-1234"}}
# File lib/action_controller/metal/strong_parameters.rb, line 247
def permit(*filters)
  params = self.class.new

  filters.flatten.each do |filter|
    case filter
    when Symbol, String
      permitted_scalar_filter(params, filter)
    when Hash then
      hash_filter(params, filter)
    end
  end

  unpermitted_parameters!(params) if self.class.action_on_unpermitted_parameters

  params.permit!
end
permit!() click to toggle source

Sets the permitted attribute to true. This can be used to pass mass assignment. Returns self.

class Person < ActiveRecord::Base
end

params = ActionController::Parameters.new(name: 'Francesco')
params.permitted?  # => false
Person.new(params) # => ActiveModel::ForbiddenAttributesError
params.permit!
params.permitted?  # => true
Person.new(params) # => #<Person id: nil, name: "Francesco">
# File lib/action_controller/metal/strong_parameters.rb, line 150
def permit!
  each_pair do |key, value|
    convert_hashes_to_parameters(key, value)
    self[key].permit! if self[key].respond_to? :permit!
  end

  @permitted = true
  self
end
permitted?() click to toggle source

Returns true if the parameter is permitted, false otherwise.

params = ActionController::Parameters.new
params.permitted? # => false
params.permit!
params.permitted? # => true
# File lib/action_controller/metal/strong_parameters.rb, line 134
def permitted?
  @permitted
end
require(key) click to toggle source

Ensures that a parameter is present. If it's present, returns the parameter at the given key, otherwise raises an ActionController::ParameterMissing error.

ActionController::Parameters.new(person: { name: 'Francesco' }).require(:person)
# => {"name"=>"Francesco"}

ActionController::Parameters.new(person: nil).require(:person)
# => ActionController::ParameterMissing: param not found: person

ActionController::Parameters.new(person: {}).require(:person)
# => ActionController::ParameterMissing: param not found: person
# File lib/action_controller/metal/strong_parameters.rb, line 172
def require(key)
  self[key].presence || raise(ParameterMissing.new(key))
end
Also aliased as: required
required(key)

Alias of require.

Alias for: require
slice(*keys) click to toggle source

Returns a new ActionController::Parameters instance that includes only the given keys. If the given keys don't exist, returns an empty hash.

params = ActionController::Parameters.new(a: 1, b: 2, c: 3)
params.slice(:a, :b) # => {"a"=>1, "b"=>2}
params.slice(:d)     # => {}
Calls superclass method
# File lib/action_controller/metal/strong_parameters.rb, line 298
def slice(*keys)
  self.class.new(super).tap do |new_instance|
    new_instance.instance_variable_set :@permitted, @permitted
  end
end

Private Instance Methods

array_of_permitted_scalars?(value) click to toggle source
# File lib/action_controller/metal/strong_parameters.rb, line 400
def array_of_permitted_scalars?(value)
  if value.is_a?(Array)
    value.all? {|element| permitted_scalar?(element)}
  end
end
array_of_permitted_scalars_filter(params, key) click to toggle source
# File lib/action_controller/metal/strong_parameters.rb, line 406
def array_of_permitted_scalars_filter(params, key)
  if has_key?(key) && array_of_permitted_scalars?(self[key])
    params[key] = self[key]
  end
end
convert_hashes_to_parameters(key, value) click to toggle source
# File lib/action_controller/metal/strong_parameters.rb, line 319
def convert_hashes_to_parameters(key, value)
  if value.is_a?(Parameters) || !value.is_a?(Hash)
    value
  else
    # Convert to Parameters on first access
    self[key] = self.class.new(value)
  end
end
each_element(object) { |el| ... } click to toggle source
# File lib/action_controller/metal/strong_parameters.rb, line 328
def each_element(object)
  if object.is_a?(Array)
    object.map { |el| yield el }.compact
  elsif object.is_a?(Hash) && object.keys.all? { |k| k =~ /\A-?\d+\z/ }
    hash = object.class.new
    object.each { |k,v| hash[k] = yield v }
    hash
  else
    yield object
  end
end
hash_filter(params, filter) click to toggle source
# File lib/action_controller/metal/strong_parameters.rb, line 413
def hash_filter(params, filter)
  filter = filter.with_indifferent_access

  # Slicing filters out non-declared keys.
  slice(*filter.keys).each do |key, value|
    return unless value

    if filter[key] == EMPTY_ARRAY
      # Declaration { comment_ids: [] }.
      array_of_permitted_scalars_filter(params, key)
    else
      # Declaration { user: :name } or { user: [:name, :age, { address: ... }] }.
      params[key] = each_element(value) do |element|
        if element.is_a?(Hash)
          element = self.class.new(element) unless element.respond_to?(:permit)
          element.permit(*Array.wrap(filter[key]))
        end
      end
    end
  end
end
permitted_scalar?(value) click to toggle source
# File lib/action_controller/metal/strong_parameters.rb, line 384
def permitted_scalar?(value)
  PERMITTED_SCALAR_TYPES.any? {|type| value.is_a?(type)}
end
permitted_scalar_filter(params, key) click to toggle source
# File lib/action_controller/metal/strong_parameters.rb, line 388
def permitted_scalar_filter(params, key)
  if has_key?(key) && permitted_scalar?(self[key])
    params[key] = self[key]
  end

  keys.grep(/\A#{Regexp.escape(key)}\(\d+[if]?\)\z/) do |k|
    if permitted_scalar?(self[k])
      params[k] = self[k]
    end
  end
end
unpermitted_keys(params) click to toggle source
# File lib/action_controller/metal/strong_parameters.rb, line 353
def unpermitted_keys(params)
  self.keys - params.keys - NEVER_UNPERMITTED_PARAMS
end
unpermitted_parameters!(params) click to toggle source
# File lib/action_controller/metal/strong_parameters.rb, line 340
def unpermitted_parameters!(params)
  unpermitted_keys = unpermitted_keys(params)
  if unpermitted_keys.any?
    case self.class.action_on_unpermitted_parameters
    when :log
      name = "unpermitted_parameters.action_controller"
      ActiveSupport::Notifications.instrument(name, keys: unpermitted_keys)
    when :raise
      raise ActionController::UnpermittedParameters.new(unpermitted_keys)
    end
  end
end