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"

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, ]

EMPTY_ARRAY = []

Attributes

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