Question

How do I list all the methods that a particular object has access to?

I have a @current_user object, defined in the application controller:

def current_user
  @current_user ||= User.find(session[:user_id]) if session[:user_id]
end

And want to see what methods I have available to me in the view file. Specifically, I want to see what methods a :has_many association provides. (I know what :has_many should provide, but want to check that.)

Answer 1

The following will list the methods that the User class has that the base Object class does not have…

>> User.methods - Object.methods
=> ["field_types", "maximum", "create!", "active_connections", "to_dropdown",
    "content_columns", "su_pw?", "default_timezone", "encode_quoted_value", 
    "reloadable?", "update", "reset_sequence_name", "default_timezone=", 
    "validate_find_options", "find_on_conditions_without_deprecation", 
    "validates_size_of", "execute_simple_calculation", "attr_protected", 
    "reflections", "table_name_prefix", ...

Note that methods is a method for Classes and for Class instances.

Here’s the methods that my User class has that are not in the ActiveRecord base class:

>> User.methods - ActiveRecord::Base.methods
=> ["field_types", "su_pw?", "set_login_attr", "create_user_and_conf_user", 
    "original_table_name", "field_type", "authenticate", "set_default_order",
    "id_name?", "id_name_column", "original_locking_column", "default_order",
    "subclass_associations",  ... 
# I ran the statements in the console.

Note that the methods created as a result of the (many) has_many relationships defined in the User class are not in the results of the methods call.

Added Note that :has_many does not add methods directly. Instead, the ActiveRecord machinery uses the Ruby method_missing and responds_to techniques to handle method calls on the fly. As a result, the methods are not listed in the methods method result.