instance method require

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