class ParameterMissing
Ruby on Rails 5.0.7.2
Since v4.0.13Raised when a required parameter is missing.
params = ActionController::Parameters.new(a: {})
params.fetch(:b)
# => ActionController::ParameterMissing: param is missing or the value is empty: b
params.require(:a)
# => ActionController::ParameterMissing: param is missing or the value is empty: a