Action Controller Parameters

Allows you 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            # => <ActionController::Parameters {"name"=>"Francesco", "age"=>22} permitted: true>
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:

  • permit_all_parameters - If it's true, all the parameters will be permitted by default. The default is false.

  • action_on_unpermitted_parameters - Allow to control the behavior when parameters that are not explicitly permitted are found. The values can be false to just filter them out, :log to additionally write a message on the logger, or :raise to raise ActionController::UnpermittedParameters exception. The default value is :log in test and development environments, false otherwise.

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 {} permitted: true>

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

Please note that these options *are not thread-safe*. In a multi-threaded environment they should only be set once at boot-time and never mutated at runtime.

You can fetch values of ActionController::Parameters using either :key or "key".

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

Methods

Constants

EMPTY_ARRAY = []
 
EMPTY_HASH = {}
 
PERMITTED_SCALAR_TYPES = [ String, Symbol, NilClass, Numeric, TrueClass, FalseClass, Date, Time, # DateTimes are Dates, we document the type but avoid the redundant check. StringIO, IO, ActionDispatch::Http::UploadedFile, Rack::Test::UploadedFile, ]
 

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.

Attributes

[R] parameters

Class Public methods

new(parameters = {})

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">
# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 235
def initialize(parameters = {})
  @parameters = parameters.with_indifferent_access
  @permitted = self.class.permit_all_parameters
end

Instance Public methods

==(other)

Returns true if another Parameters object contains the same content and permitted flag.

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 242
def ==(other)
  if other.respond_to?(:permitted?)
    permitted? == other.permitted? && parameters == other.parameters
  else
    @parameters == other
  end
end

[](key)

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

params = ActionController::Parameters.new(person: { name: "Francesco" })
params[:person] # => <ActionController::Parameters {"name"=>"Francesco"} permitted: false>
params[:none]   # => nil
# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 551
def [](key)
  convert_hashes_to_parameters(key, @parameters[key])
end

[]=(key, value)

Assigns a value to a given key. The given key may still get filtered out when permit is called.

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 557
def []=(key, value)
  @parameters[key] = value
end

as_json(options=nil)

Returns a hash that can be used as the JSON representation for the parameters.

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 129
    

converted_arrays()

Attribute that keeps track of converted arrays, if any, to avoid double looping in the common use case permit + mass-assignment. Defined in a method to instantiate it only if needed.

Testing membership still loops, but it's going to be faster than our own loop that converts values. Also, we are not going to build a new array object per fetch.

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 350
def converted_arrays
  @converted_arrays ||= Set.new
end

deep_dup()

Returns duplicate of object including all parameters.

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 790
def deep_dup
  self.class.new(@parameters.deep_dup).tap do |duplicate|
    duplicate.permitted = @permitted
  end
end

delete(key, &block)

Deletes a key-value pair from Parameters and returns the value. If key is not found, returns nil (or, with optional code block, yields key and returns the result). Cf. #extract!, which returns the corresponding ActionController::Parameters object.

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 683
def delete(key, &block)
  convert_value_to_parameters(@parameters.delete(key, &block))
end

delete_if(&block)

Alias for: reject!

dig(*keys)

Extracts the nested parameter from the given keys by calling dig at each step. Returns nil if any intermediate step is nil.

params = ActionController::Parameters.new(foo: { bar: { baz: 1 } })
params.dig(:foo, :bar, :baz) # => 1
params.dig(:foo, :zot, :xyz) # => nil

params2 = ActionController::Parameters.new(foo: [10, 11, 12])
params2.dig(:foo, 1) # => 11
# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 596
def dig(*keys)
  convert_hashes_to_parameters(keys.first, @parameters[keys.first])
  @parameters.dig(*keys)
end

each(&block)

Alias for: each_pair

each_pair(&block)

Convert all hashes in values into parameters, then yield each pair in the same way as Hash#each_pair.

Also aliased as: each
# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 336
def each_pair(&block)
  @parameters.each_pair do |key, value|
    yield [key, convert_hashes_to_parameters(key, value)]
  end
end

empty?()

Returns true if the parameters have no key/value pairs.

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 137
    

except(*keys)

Returns a new ActionController::Parameters instance that filters out the given keys.

params = ActionController::Parameters.new(a: 1, b: 2, c: 3)
params.except(:a, :b) # => <ActionController::Parameters {"c"=>3} permitted: false>
params.except(:d)     # => <ActionController::Parameters {"a"=>1, "b"=>2, "c"=>3} permitted: false>
# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 626
def except(*keys)
  new_instance_with_inherited_permitted_status(@parameters.except(*keys))
end

extract!(*keys)

Removes and returns the key/value pairs matching the given keys.

params = ActionController::Parameters.new(a: 1, b: 2, c: 3)
params.extract!(:a, :b) # => <ActionController::Parameters {"a"=>1, "b"=>2} permitted: false>
params                  # => <ActionController::Parameters {"c"=>3} permitted: false>
# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 635
def extract!(*keys)
  new_instance_with_inherited_permitted_status(@parameters.extract!(*keys))
end

fetch(key, *args)

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 a second argument is given, then that is returned (converted to an instance of ActionController::Parameters if possible); if a block is given, then that will be run and its result returned.

params = ActionController::Parameters.new(person: { name: "Francesco" })
params.fetch(:person)               # => <ActionController::Parameters {"name"=>"Francesco"} permitted: false>
params.fetch(:none)                 # => ActionController::ParameterMissing: param is missing or the value is empty: none
params.fetch(:none, {})             # => <ActionController::Parameters {} permitted: false>
params.fetch(:none, "Francesco")    # => "Francesco"
params.fetch(:none) { "Francesco" } # => "Francesco"
# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 574
def fetch(key, *args)
  convert_value_to_parameters(
    @parameters.fetch(key) {
      if block_given?
        yield
      else
        args.fetch(0) { raise ActionController::ParameterMissing.new(key) }
      end
    }
  )
end

has_key?(key)

Returns true if the given key is present in the parameters.

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 145
    

has_value?(value)

Returns true if the given value is present for some key in the parameters.

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 153
    

include?(key)

Returns true if the given key is present in the parameters.

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 161
    

inspect()

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 758
def inspect
  "<#{self.class} #{@parameters} permitted: #{@permitted}>"
end

keep_if(&block)

Alias for: select!

key?(key)

Returns true if the given key is present in the parameters.

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 169
    

keys()

Returns a new array of the keys of the parameters.

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 177
    

merge(other_hash)

Returns a new ActionController::Parameters with all keys from other_hash merged into current hash.

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 721
def merge(other_hash)
  new_instance_with_inherited_permitted_status(
    @parameters.merge(other_hash.to_h)
  )
end

merge!(other_hash)

Returns current ActionController::Parameters instance with other_hash merged into current hash.

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 729
def merge!(other_hash)
  @parameters.merge!(other_hash.to_h)
  self
end

permit(*filters)

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 if 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 = ActionController::Parameters.new(tags: ["rails", "parameters"])
params.permit(tags: [])

Sometimes it is not possible or convenient to declare the valid keys of a hash parameter or its internal structure. Just map to an empty hash:

params.permit(preferences: {})

Be careful because this opens the door to arbitrary input. In this case, permit ensures values in the returned structure are permitted scalars and filters out anything else.

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)
# => <ActionController::Parameters {} permitted: true>

params.require(:person).permit(contact: :phone)
# => <ActionController::Parameters {"contact"=><ActionController::Parameters {"phone"=>"555-1234"} permitted: true>} permitted: true>

params.require(:person).permit(contact: [ :email, :phone ])
# => <ActionController::Parameters {"contact"=><ActionController::Parameters {"email"=>"none@test.com", "phone"=>"555-1234"} permitted: true>} permitted: true>
# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 528
def permit(*filters)
  params = self.class.new

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

  unpermitted_parameters!(params) if self.class.action_on_unpermitted_parameters

  params.permit!
end

permit!()

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 actionpack/lib/action_controller/metal/strong_parameters.rb, line 376
def permit!
  each_pair do |key, value|
    Array.wrap(value).flatten.each do |v|
      v.permit! if v.respond_to? :permit!
    end
  end

  @permitted = true
  self
end

permitted?()

Returns true if the parameter is permitted, false otherwise.

params = ActionController::Parameters.new
params.permitted? # => false
params.permit!
params.permitted? # => true
# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 360
def permitted?
  @permitted
end

reject(&block)

Returns a new instance of ActionController::Parameters with items that the block evaluates to true removed.

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 702
def reject(&block)
  new_instance_with_inherited_permitted_status(@parameters.reject(&block))
end

reject!(&block)

Removes items that the block evaluates to true and returns self.

Also aliased as: delete_if
# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 707
def reject!(&block)
  @parameters.reject!(&block)
  self
end

require(key)

This method accepts both a single key and an array of keys.

When passed a single key, if it exists and its associated value is either present or the singleton false, returns said value:

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

Otherwise raises ActionController::ParameterMissing:

ActionController::Parameters.new.require(:person)
# ActionController::ParameterMissing: param is missing or the value is empty: person

ActionController::Parameters.new(person: nil).require(:person)
# ActionController::ParameterMissing: param is missing or the value is empty: person

ActionController::Parameters.new(person: "\t").require(:person)
# ActionController::ParameterMissing: param is missing or the value is empty: person

ActionController::Parameters.new(person: {}).require(:person)
# ActionController::ParameterMissing: param is missing or the value is empty: person

When given an array of keys, the method tries to require each one of them in order. If it succeeds, an array with the respective return values is returned:

params = ActionController::Parameters.new(user: { ... }, profile: { ... })
user_params, profile_params = params.require([:user, :profile])

Otherwise, the method re-raises the first exception found:

params = ActionController::Parameters.new(user: {}, profile: {})
user_params, profile_params = params.require([:user, :profile])
# ActionController::ParameterMissing: param is missing or the value is empty: user

Technically this method can be used to fetch terminal values:

# CAREFUL
params = ActionController::Parameters.new(person: { name: "Finn" })
name = params.require(:person).require(:name) # CAREFUL

but take into account that at some point those ones have to be permitted:

def person_params
  params.require(:person).permit(:name).tap do |person_params|
    person_params.require(:name) # SAFER
  end
end

for example.

Also aliased as: required
# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 437
def require(key)
  return key.map { |k| require(k) } if key.is_a?(Array)
  value = self[key]
  if value.present? || value == false
    value
  else
    raise ParameterMissing.new(key)
  end
end

required(key)

Alias of require.

Alias for: require

reverse_merge(other_hash)

Returns a new ActionController::Parameters with all keys from current hash merged into other_hash.

Also aliased as: with_defaults
# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 736
def reverse_merge(other_hash)
  new_instance_with_inherited_permitted_status(
    other_hash.to_h.merge(@parameters)
  )
end

reverse_merge!(other_hash)

Returns current ActionController::Parameters instance with current hash merged into other_hash.

Also aliased as: with_defaults!
# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 745
def reverse_merge!(other_hash)
  @parameters.merge!(other_hash.to_h) { |key, left, right| left }
  self
end

select(&block)

Returns a new instance of ActionController::Parameters with only items that the block evaluates to true.

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 689
def select(&block)
  new_instance_with_inherited_permitted_status(@parameters.select(&block))
end

select!(&block)

Equivalent to Hash#keep_if, but returns nil if no changes were made.

Also aliased as: keep_if
# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 694
def select!(&block)
  @parameters.select!(&block)
  self
end

slice(*keys)

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) # => <ActionController::Parameters {"a"=>1, "b"=>2} permitted: false>
params.slice(:d)     # => <ActionController::Parameters {} permitted: false>
# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 609
def slice(*keys)
  new_instance_with_inherited_permitted_status(@parameters.slice(*keys))
end

slice!(*keys)

Returns current ActionController::Parameters instance which contains only the given keys.

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 615
def slice!(*keys)
  @parameters.slice!(*keys)
  self
end

to_h()

Returns a safe ActiveSupport::HashWithIndifferentAccess representation of the parameters with all unpermitted keys removed.

params = ActionController::Parameters.new({
  name: "Senjougahara Hitagi",
  oddity: "Heavy stone crab"
})
params.to_h
# => ActionController::UnfilteredParameters: unable to convert unpermitted parameters to hash

safe_params = params.permit(:name)
safe_params.to_h # => {"name"=>"Senjougahara Hitagi"}
# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 262
def to_h
  if permitted?
    convert_parameters_to_hashes(@parameters, :to_h)
  else
    raise UnfilteredParameters
  end
end

to_hash()

Returns a safe Hash representation of the parameters with all unpermitted keys removed.

params = ActionController::Parameters.new({
  name: "Senjougahara Hitagi",
  oddity: "Heavy stone crab"
})
params.to_hash
# => ActionController::UnfilteredParameters: unable to convert unpermitted parameters to hash

safe_params = params.permit(:name)
safe_params.to_hash # => {"name"=>"Senjougahara Hitagi"}
# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 282
def to_hash
  to_h.to_hash
end

to_param(*args)

Alias for: to_query

to_query(*args)

Returns a string representation of the receiver suitable for use as a URL query string:

params = ActionController::Parameters.new({
  name: "David",
  nationality: "Danish"
})
params.to_query
# => ActionController::UnfilteredParameters: unable to convert unpermitted parameters to hash

safe_params = params.permit(:name, :nationality)
safe_params.to_query
# => "name=David&nationality=Danish"

An optional namespace can be passed to enclose key names:

params = ActionController::Parameters.new({
  name: "David",
  nationality: "Danish"
})
safe_params = params.permit(:name, :nationality)
safe_params.to_query("user")
# => "user%5Bname%5D=David&user%5Bnationality%5D=Danish"

The string pairs “key=value” that conform the query string are sorted lexicographically in ascending order.

This method is also aliased as to_param.

Also aliased as: to_param
# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 314
def to_query(*args)
  to_h.to_query(*args)
end

to_s()

Returns the content of the parameters as a string.

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 185
    

to_unsafe_h()

Returns an unsafe, unfiltered ActiveSupport::HashWithIndifferentAccess representation of the parameters.

params = ActionController::Parameters.new({
  name: "Senjougahara Hitagi",
  oddity: "Heavy stone crab"
})
params.to_unsafe_h
# => {"name"=>"Senjougahara Hitagi", "oddity" => "Heavy stone crab"}
Also aliased as: to_unsafe_hash
# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 329
def to_unsafe_h
  convert_parameters_to_hashes(@parameters, :to_unsafe_h)
end

to_unsafe_hash()

Alias for: to_unsafe_h

transform_keys(&block)

Returns a new ActionController::Parameters instance with the results of running block once for every key. The values are unchanged.

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 662
def transform_keys(&block)
  if block
    new_instance_with_inherited_permitted_status(
      @parameters.transform_keys(&block)
    )
  else
    @parameters.transform_keys
  end
end

transform_keys!(&block)

Performs keys transformation and returns the altered ActionController::Parameters instance.

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 674
def transform_keys!(&block)
  @parameters.transform_keys!(&block)
  self
end

transform_values()

Returns a new ActionController::Parameters with the results of running block once for every value. The keys are unchanged.

params = ActionController::Parameters.new(a: 1, b: 2, c: 3)
params.transform_values { |x| x * 2 }
# => <ActionController::Parameters {"a"=>2, "b"=>4, "c"=>6} permitted: false>
# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 645
def transform_values
  return to_enum(:transform_values) unless block_given?
  new_instance_with_inherited_permitted_status(
    @parameters.transform_values { |v| yield convert_value_to_parameters(v) }
  )
end

transform_values!()

Performs values transformation and returns the altered ActionController::Parameters instance.

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 654
def transform_values!
  return to_enum(:transform_values!) unless block_given?
  @parameters.transform_values! { |v| yield convert_value_to_parameters(v) }
  self
end

value?(value)

Returns true if the given value is present for some key in the parameters.

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 193
    

values()

Returns a new array of the values of the parameters.

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 207
delegate :keys, :key?, :has_key?, :values, :has_value?, :value?, :empty?, :include?,
  :as_json, :to_s, to: :@parameters

values_at(*keys)

Returns values that were assigned to the given keys. Note that all the Hash objects will be converted to ActionController::Parameters.

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 715
def values_at(*keys)
  convert_value_to_parameters(@parameters.values_at(*keys))
end

with_defaults(other_hash)

Alias for: reverse_merge

with_defaults!(other_hash)

Alias for: reverse_merge!

Instance Protected methods

fields_for_style?()

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 803
def fields_for_style?
  @parameters.all? { |k, v| k =~ /\A-?\d+\z/ && (v.is_a?(Hash) || v.is_a?(Parameters)) }
end

permitted=(new_permitted)

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 799
def permitted=(new_permitted)
  @permitted = new_permitted
end