Returns a new ActionController::Parameters instance. 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 287
def initialize(parameters = {}, logging_context = {})
  parameters.each_key do |key|
    unless key.is_a?(String) || key.is_a?(Symbol)
      raise InvalidParameterKey, "all keys must be Strings or Symbols, got: #{key.class}"
    end
  end

  @parameters = parameters.with_indifferent_access
  @logging_context = logging_context
  @permitted = self.class.permit_all_parameters
end

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

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 301
def ==(other)
  if other.respond_to?(:permitted?)
    permitted? == other.permitted? && parameters == other.parameters
  else
    super
  end
end

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 797
def [](key)
  convert_hashes_to_parameters(key, @parameters[key])
end

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 803
def []=(key, value)
  @parameters[key] = value
end

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

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 194
    

Returns a new ActionController::Parameters instance with nil values removed.

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 974
def compact
  new_instance_with_inherited_permitted_status(@parameters.compact)
end

Removes all nil values in place and returns self, or nil if no changes were made.

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 980
def compact!
  self if @parameters.compact!
end

Returns a new ActionController::Parameters instance without the blank values. Uses Object#blank? for determining if a value is blank.

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 986
def compact_blank
  reject { |_k, v| v.blank? }
end

Removes all blank values in place and returns self. Uses Object#blank? for determining if a value is blank.

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 992
def compact_blank!
  reject! { |_k, v| v.blank? }
end

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 435
def converted_arrays
  @converted_arrays ||= Set.new
end

Returns a duplicate ActionController::Parameters instance with the same permitted parameters.

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 1092
def deep_dup
  self.class.new(@parameters.deep_dup, @logging_context).tap do |duplicate|
    duplicate.permitted = @permitted
  end
end

Returns a new ActionController::Parameters instance with self and other_hash merged recursively.

Like with Hash#merge in the standard library, a block can be provided to merge values.

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 168
    

Same as deep_merge, but modifies self.

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 183
    

Returns a new ActionController::Parameters instance with the results of running block once for every key. This includes the keys from the root hash and from all nested hashes and arrays. The values are unchanged.

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 924
def deep_transform_keys(&block)
  new_instance_with_inherited_permitted_status(
    _deep_transform_keys_in_object(@parameters, &block).to_unsafe_h
  )
end

Returns the same ActionController::Parameters instance with changed keys. This includes the keys from the root hash and from all nested hashes and arrays. The values are unchanged.

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 933
def deep_transform_keys!(&block)
  @parameters = _deep_transform_keys_in_object(@parameters, &block).to_unsafe_h
  self
end

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). This method is similar to extract!, which returns the corresponding ActionController::Parameters object.

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 942
def delete(key, &block)
  convert_value_to_parameters(@parameters.delete(key, &block))
end

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 841
def dig(*keys)
  convert_hashes_to_parameters(keys.first, @parameters[keys.first])
  @parameters.dig(*keys)
end

Calls block once for each key in the parameters, passing the key. If no block is given, an enumerator is returned instead.

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 202
    

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

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 402
def each_pair(&block)
  return to_enum(__callee__) unless block_given?
  @parameters.each_pair do |key, value|
    yield [key, convert_hashes_to_parameters(key, value)]
  end

  self
end

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

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 414
def each_value(&block)
  return to_enum(:each_value) unless block_given?
  @parameters.each_pair do |key, value|
    yield convert_hashes_to_parameters(key, value)
  end

  self
end

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

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 211
    

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 869
def except(*keys)
  new_instance_with_inherited_permitted_status(@parameters.except(*keys))
end

Returns true if the given key is not present in the parameters.

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 219
    

expect is the preferred way to require and permit parameters. It is safer than the previous recommendation to call permit and require in sequence, which could allow user triggered 500 errors.

expect is more strict with types to avoid a number of potential pitfalls that may be encountered with the .require.permit pattern.

For example:

params = ActionController::Parameters.new(comment: { text: "hello" })
params.expect(comment: [:text])
# => #<ActionController::Parameters { text: "hello" } permitted: true>

params = ActionController::Parameters.new(comment: [{ text: "hello" }, { text: "world" }])
params.expect(comment: [:text])
# => ActionController::ParameterMissing: param is missing or the value is empty or invalid: comment

In order to permit an array of parameters, the array must be defined explicitly. Use double array brackets, an array inside an array, to declare that an array of parameters is expected.

params = ActionController::Parameters.new(comments: [{ text: "hello" }, { text: "world" }])
params.expect(comments: [[:text]])
# => [#<ActionController::Parameters { "text" => "hello" } permitted: true>,
#     #<ActionController::Parameters { "text" => "world" } permitted: true>]

params = ActionController::Parameters.new(comments: { text: "hello" })
params.expect(comments: [[:text]])
# => ActionController::ParameterMissing: param is missing or the value is empty or invalid: comments

expect is intended to protect against array tampering.

params = ActionController::Parameters.new(user: "hack")
# The previous way of requiring and permitting parameters will error
params.require(:user).permit(:name, pets: [:name]) # wrong
# => NoMethodError: undefined method `permit' for an instance of String

# similarly with nested parameters
params = ActionController::Parameters.new(user: { name: "Martin", pets: { name: "hack" } })
user_params = params.require(:user).permit(:name, pets: [:name]) # wrong
# user_params[:pets] is expected to be an array but is a hash

expect solves this by being more strict with types.

params = ActionController::Parameters.new(user: "hack")
params.expect(user: [ :name, pets: [[:name]] ])
# => ActionController::ParameterMissing: param is missing or the value is empty or invalid: user

# with nested parameters
params = ActionController::Parameters.new(user: { name: "Martin", pets: { name: "hack" } })
user_params = params.expect(user: [:name, pets: [[:name]] ])
user_params[:pets] # => nil

As the examples show, expect requires the :user key, and any root keys similar to the .require.permit pattern. If multiple root keys are expected, they will all be required.

params = ActionController::Parameters.new(name: "Martin", pies: [{ type: "dessert", flavor: "pumpkin"}])
name, pies = params.expect(:name, pies: [[:type, :flavor]])
name # => "Martin"
pies # => [#<ActionController::Parameters {"type"=>"dessert", "flavor"=>"pumpkin"} permitted: true>]

When called with a hash with multiple keys, expect will permit the parameters and require the keys in the order they are given in the hash, returning an array of the permitted parameters.

params = ActionController::Parameters.new(subject: { name: "Martin" }, object: { pie: "pumpkin" })
subject, object = params.expect(subject: [:name], object: [:pie])
subject # => #<ActionController::Parameters {"name"=>"Martin"} permitted: true>
object  # => #<ActionController::Parameters {"pie"=>"pumpkin"} permitted: true>

Besides being more strict about array vs hash params, expect uses permit internally, so it will behave similarly.

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

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

An array of permitted scalars may be expected with the following:

params = ActionController::Parameters.new(tags: ["rails", "parameters"])
permitted = params.expect(tags: [])
permitted                 # => ["rails", "parameters"]
permitted.is_a?(Array)    # => true
permitted.size            # => 2

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 772
def expect(*filters)
  params = permit_filters(filters)
  keys = filters.flatten.flat_map { |f| f.is_a?(Hash) ? f.keys : f }
  values = params.require(keys)
  values.size == 1 ? values.first : values
end

Same as expect, but raises an ActionController::ExpectedParameterMissing instead of ActionController::ParameterMissing. Unlike expect which will render a 400 response, expect! will raise an exception that is not handled. This is intended for debugging invalid params for an internal API where incorrectly formatted params would indicate a bug in a client library that should be fixed.

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 786
def expect!(*filters)
  expect(*filters)
rescue ParameterMissing => e
  raise ExpectedParameterMissing.new(e.param, e.keys)
end

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 879
def extract!(*keys)
  new_instance_with_inherited_permitted_status(@parameters.extract!(*keys))
end

Returns parameter value for the given key separated by delimiter.

params = ActionController::Parameters.new(id: "1_123", tags: "ruby,rails")
params.extract_value(:id) # => ["1", "123"]
params.extract_value(:tags, delimiter: ",") # => ["ruby", "rails"]
params.extract_value(:non_existent_key) # => nil

Note that if the given key‘s value contains blank elements, then the returned array will include empty strings.

params = ActionController::Parameters.new(tags: "ruby,rails,,web")
params.extract_value(:tags, delimiter: ",") # => ["ruby", "rails", "", "web"]

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 1110
def extract_value(key, delimiter: "_")
  @parameters[key]&.split(delimiter, -1)
end

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 or invalid: 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 820
def fetch(key, *args)
  convert_value_to_parameters(
    @parameters.fetch(key) {
      if block_given?
        yield
      else
        args.fetch(0) { raise ActionController::ParameterMissing.new(key, @parameters.keys) }
      end
    }
  )
end

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

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 997
def has_value?(value)
  each_value.include?(convert_value_to_parameters(value))
end

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

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 227
    

Returns a new array of the keys of the parameters.

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 235
    

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

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 1011
def merge(other_hash)
  new_instance_with_inherited_permitted_status(
    @parameters.merge(other_hash.to_h)
  )
end

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

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 1022
def merge!(other_hash, &block)
  @parameters.merge!(other_hash.to_h, &block)
  self
end

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(name: "Francesco", age: 22, role: "admin")
permitted = params.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:

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

This has the added benefit of rejecting user-modified inputs that send a string when a hash is expected.

When followed by require, you can both filter and require parameters following the typical pattern of a Rails form. The expect method was made specifically for this use case and is the recommended way to require and permit parameters.

 permitted = params.expect(person: [:name, :age])

When using permit and require separately, pay careful attention to the order of the method calls.

 params = ActionController::Parameters.new(person: { name: "Martin", age: 40, role: "admin" })
 permitted = params.permit(person: [:name, :age]).require(:person) # correct

When require is used first, it is possible for users of your application to trigger a NoMethodError when the user, for example, sends a string for :person.

 params = ActionController::Parameters.new(person: "tampered")
 permitted = params.require(:person).permit(:name, :age) # not recommended
 # => NoMethodError: undefined method `permit' for an instance of String

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 permitted.

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

params.permit(person: :contact).require(:person)
# => ActionController::ParameterMissing: param is missing or the value is empty or invalid: person

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

params.permit(person: { contact: [ :email, :phone ] }).require(:person)
# => #<ActionController::Parameters {"contact"=>#<ActionController::Parameters {"email"=>"none@test.com", "phone"=>"555-1234"} permitted: true>} permitted: true>

If your parameters specify multiple parameters indexed by a number, you can permit each set of parameters under the numeric key to be the same using the same syntax as permitting a single item.

params = ActionController::Parameters.new({
  person: {
    '0': {
      email: "none@test.com",
      phone: "555-1234"
    },
    '1': {
      email: "nothing@test.com",
      phone: "555-6789"
    },
  }
})
params.permit(person: [:email]).to_h
# => {"person"=>{"0"=>{"email"=>"none@test.com"}, "1"=>{"email"=>"nothing@test.com"}}}

If you want to specify what keys you want from each numeric key, you can instead specify each one individually

params = ActionController::Parameters.new({
  person: {
    '0': {
      email: "none@test.com",
      phone: "555-1234"
    },
    '1': {
      email: "nothing@test.com",
      phone: "555-6789"
    },
  }
})
params.permit(person: { '0': [:email], '1': [:phone]}).to_h
# => {"person"=>{"0"=>{"email"=>"none@test.com"}, "1"=>{"phone"=>"555-6789"}}}

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 668
def permit(*filters)
  permit_filters(filters, on_unpermitted: self.class.action_on_unpermitted_parameters, explicit_arrays: false)
end

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 461
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

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 445
def permitted?
  @permitted
end

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

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 961
def reject(&block)
  new_instance_with_inherited_permitted_status(@parameters.reject(&block))
end

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

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 966
def reject!(&block)
  @parameters.reject!(&block)
  self
end

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 or invalid: person

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

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

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

This method is not recommended for fetching terminal values because it does not permit the values. For example, this can cause problems:

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

It is recommended to use expect instead:

def person_params
  params.expect(person: :name).require(:name)
end

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 519
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, @parameters.keys)
  end
end

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

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 1033
def reverse_merge(other_hash)
  new_instance_with_inherited_permitted_status(
    other_hash.to_h.merge(@parameters)
  )
end

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

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 1042
def reverse_merge!(other_hash)
  @parameters.merge!(other_hash.to_h) { |key, left, right| left }
  self
end

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

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 948
def select(&block)
  new_instance_with_inherited_permitted_status(@parameters.select(&block))
end

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

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 953
def select!(&block)
  @parameters.select!(&block)
  self
end

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 852
def slice(*keys)
  new_instance_with_inherited_permitted_status(@parameters.slice(*keys))
end

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

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 858
def slice!(*keys)
  @parameters.slice!(*keys)
  self
end

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 331
def to_h(&block)
  if permitted?
    convert_parameters_to_hashes(@parameters, :to_h, &block)
  else
    raise UnfilteredParameters
  end
end

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 351
def to_hash
  to_h.to_hash
end

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.

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 381
def to_query(*args)
  to_h.to_query(*args)
end

Returns the content of the parameters as a string.

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 250
delegate :keys, :empty?, :exclude?, :include?,
  :as_json, :to_s, :each_key, to: :@parameters

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"}

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 395
def to_unsafe_h
  convert_parameters_to_hashes(@parameters, :to_unsafe_h)
end

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 906
def transform_keys(&block)
  return to_enum(:transform_keys) unless block_given?
  new_instance_with_inherited_permitted_status(
    @parameters.transform_keys(&block)
  )
end

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

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 915
def transform_keys!(&block)
  return to_enum(:transform_keys!) unless block_given?
  @parameters.transform_keys!(&block)
  self
end

Returns a new ActionController::Parameters instance 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 889
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

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

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 898
def transform_values!
  return to_enum(:transform_values!) unless block_given?
  @parameters.transform_values! { |v| yield convert_value_to_parameters(v) }
  self
end

Returns a new array of the values of the parameters.

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 424
def values
  to_enum(:each_value).to_a
end

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 1005
def values_at(*keys)
  convert_value_to_parameters(@parameters.values_at(*keys))
end

Filters self and optionally checks for unpermitted keys

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 1130
def permit_filters(filters, on_unpermitted: nil, explicit_arrays: true)
  params = self.class.new

  filters.flatten.each do |filter|
    case filter
    when Symbol, String
      # Declaration [:name, "age"]
      permitted_scalar_filter(params, filter)
    when Hash
      # Declaration [{ person: ... }]
      hash_filter(params, filter, on_unpermitted:, explicit_arrays:)
    end
  end

  unpermitted_parameters!(params, on_unpermitted:)

  params.permit!
end