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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:

  • 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 :log to 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.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.

ActionController::Parameters inherits 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"
Methods
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Constants
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.

EMPTY_ARRAY = []
 
Class Public methods
const_missing(const_name)
# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 123
    def self.const_missing(const_name)
      return super unless const_name == :NEVER_UNPERMITTED_PARAMS
      ActiveSupport::Deprecation.warn("        `ActionController::Parameters::NEVER_UNPERMITTED_PARAMS` has been deprecated.
        Use `ActionController::Parameters.always_permitted_parameters` instead.
".squish)

      always_permitted_parameters
    end
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 149
def initialize(parameters = {})
  @parameters = parameters.with_indifferent_access
  @permitted = self.class.permit_all_parameters
end
Instance Public methods
==(other_hash)

Returns true if another Parameters object contains the same content and permitted flag, or other Hash-like object contains the same content. This override is in place so you can perform a comparison with `Hash`.

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 157
def ==(other_hash)
  if other_hash.respond_to?(:permitted?)
    super
  else
    @parameters == other_hash
  end
end
[](key)

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
# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 398
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 404
def []=(key, value)
  @parameters[key] = value
end
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 206
def converted_arrays
  @converted_arrays ||= Set.new
end
delete(key, &block)

Deletes and returns a key-value pair from Parameters whose key is equal to key. If the key is not found, returns the default value. If the optional code block is given and the key is not found, pass in the key and return the result of block.

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 514
def delete(key, &block)
  convert_value_to_parameters(@parameters.delete(key))
end
delete_if(&block)
Alias for: reject!
dup()

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
# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 558
def dup
  super.tap do |duplicate|
    duplicate.permitted = @permitted
  end
end
each(&block)
Alias for: each_pair
each_pair(&block)

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

Also aliased as: each
# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 192
def each_pair(&block)
  @parameters.each_pair do |key, value|
    yield key, convert_hashes_to_parameters(key, value)
  end
end
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) # => {"c"=>3}
params.except(:d)     # => {"a"=>1,"b"=>2,"c"=>3}
# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 455
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) # => {"a"=>1, "b"=>2}
params                  # => {"c"=>3}
# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 464
def extract!(*keys)
  new_instance_with_inherited_permitted_status(@parameters.extract!(*keys))
end
fetch(key, *args, &block)

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 is missing or the value is empty: none
params.fetch(:none, 'Francesco')    # => "Francesco"
params.fetch(:none) { 'Francesco' } # => "Francesco"
# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 419
def fetch(key, *args, &block)
  convert_value_to_parameters(
    @parameters.fetch(key) {
      if block_given?
        yield
      else
        args.fetch(0) { raise ActionController::ParameterMissing.new(key) }
      end
    }
  )
end
keep_if(&block)
Alias for: select!
merge(other_hash)

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

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 566
def merge(other_hash)
  new_instance_with_inherited_permitted_status(
    @parameters.merge(other_hash)
  )
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: [])

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 actionpack/lib/action_controller/metal/strong_parameters.rb, line 375
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!()

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 232
def permit!
  each_pair do |key, value|
    Array.wrap(value).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 216
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 533
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 538
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)
# => {"name"=>"Francesco"}

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 reraises 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 293
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
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 520
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 525
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) # => {"a"=>1, "b"=>2}
params.slice(:d)     # => {}
# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 438
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 444
def slice!(*keys)
  @parameters.slice!(*keys)
  self
end
to_h()

Returns a safe Hash representation of this parameter with all unpermitted keys removed.

params = ActionController::Parameters.new({
  name: 'Senjougahara Hitagi',
  oddity: 'Heavy stone crab'
})
params.to_h # => {}

safe_params = params.permit(:name)
safe_params.to_h # => {"name"=>"Senjougahara Hitagi"}
# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 176
def to_h
  if permitted?
    @parameters.to_h
  else
    slice(*self.class.always_permitted_parameters).permit!.to_h
  end
end
to_unsafe_h()

Returns an unsafe, unfiltered Hash representation of this parameter.

Also aliased as: to_unsafe_hash
# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 185
def to_unsafe_h
  @parameters.to_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 493
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 505
def transform_keys!(&block)
  @parameters.transform_keys!(&block)
  self
end
transform_values(&block)

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 }
# => {"a"=>2, "b"=>4, "c"=>6}
# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 474
def transform_values(&block)
  if block
    new_instance_with_inherited_permitted_status(
      @parameters.transform_values(&block)
    )
  else
    @parameters.transform_values
  end
end
transform_values!(&block)

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

# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 486
def transform_values!(&block)
  @parameters.transform_values!(&block)
  self
end
values_at(*keys)

Return 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 546
def values_at(*keys)
  convert_value_to_parameters(@parameters.values_at(*keys))
end
Instance Protected methods
fields_for_style?()
# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 584
def fields_for_style?
  @parameters.all? { |k, v| k =~ /\A-?\d+\z/ && v.is_a?(Hash) }
end
permitted=(new_permitted)
# File actionpack/lib/action_controller/metal/strong_parameters.rb, line 580
def permitted=(new_permitted)
  @permitted = new_permitted
end