class AdminController < ActionController::Base
  # It will raise an ActiveModel::ForbiddenAttributes exception for using mass assignment
  def create
    Admin.create(params[:admin])
  end
 
  # Here it will pass as long as it has admin key and will throw 
  #    ActionController::ParameterMissing if it will not get
  # here we are not doing mass assignment on update
  def update
    admin = Admin.find(params[:id])
    admin.update!(admin_params)
    redirect_to admin
  end
 
  private
    # Here we are permitting the admin_params to be passed in to the ActiveModel
    def admin_params
      params.require(:admin).permit(:name, :role, :contact, :position)
    end
end

Rails allows you to permit scalar values,i.e. :id, so that anything other than this like array, hashes or object can't be injected into it. Permitted scalar types are: String, Symbol, NilClass, Numeric, TrueClass, FalseClass, Date, Time, DateTime, StringIO, IO, ActionDispatch::Http::UploadedFile, and Rack::Test::UploadedFile.

# To whitelist id
params.permit(:id)

# If the value in params needed to be an array of permitted scalar values 
params.permit(id: [])

# To permit an entire hash of parameters
params.require(:entries).permit!

# To permit nested parameters, you can define them like this
params.permit(:name, { contacts: [] },
              managers: [ :name,
                         { projects: [ :name ], categories: [] }])

You can use fetch to supply a default and use Strong Parameter API :

params.fetch(:master, {}).permit(:name, :specialization)

To deal with accepts_nested_attributes_for in combination with has_many association, you can use it as:

# To whitelist the following data:
# {
#    "blog" => {
#              "title" => "Rails Applications",
#             "categories" => { 
#                              "1" => {"cat-name" => "Form Helpers"},
#                             "2" => {"cat-name" => "Associations"}
#                              }
#              }
#  }
 
params.require(:blog).permit(:title, categories: [:cat-name])

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