Class: ActionController::Parameters

By default, never raise an UnpermittedParameters exception if these params are present. The default includes both ‘controller’ and ‘action’ because they are added by ::Rails and should be of no concern. One way to change these is to specify always_permitted_parameters in your config. For instance:

config.action_controller.always_permitted_parameters = %w( controller action format )

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

Alias for #include?.

Alias for #include?.

Returns a new array of the keys of the parameters.

Alias for #include?.

Returns true if the parameter is permitted, false otherwise.

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

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

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

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

Returns a new Parameters instance with nil values removed.

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

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

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

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.

Returns a duplicate Parameters instance with the same permitted parameters.

Returns a new 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.

Same as #deep_merge, but modifies self.

Returns a new 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.

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

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 Parameters object.

Alias for #reject!.

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

Alias for #each_pair.

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

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

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

Returns a new 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>

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

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.permitted?      # => true
permitted.is_a?(Array)    # => true
permitted.size            # => 2

Same as #expect, but raises an ExpectedParameterMissing instead of 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.

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>

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"]

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 ParameterMissing error; if a second argument is given, then that is returned (converted to an instance of 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"

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

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

Alias for #select!.

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

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

Returns a new 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::Parameters {} permitted: true>

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"}}}

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">

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

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

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 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

Alias for #require.

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

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

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

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

Returns a new 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>

Returns the current Parameters instance which contains only the given #keys.

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"}

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"}

Alias for #to_query.

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.

Returns the content of the parameters as a string.

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"}

Alias for #to_unsafe_h.

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

Performs keys transformation and returns the altered Parameters instance.

Returns a new 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>

Performs values transformation and returns the altered Parameters instance.

Alias for #has_value?.

Returns a new array of the values of the parameters.

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

Alias for #reverse_merge.

Alias for #reverse_merge!.

Alias for #except.