How to list all methods for an object in Ruby?
Ruby on-RailsRubyRuby on-Rails Problem Overview
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.)
Ruby on-Rails Solutions
Solution 1 - Ruby on-Rails
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.
Solution 2 - Ruby on-Rails
Or just User.methods(false)
to return only the methods defined within that class.
Solution 3 - Ruby on-Rails
> Returns an array containing the names of the public and protected instance methods in the receiver. For a module, these are the public and protected methods; for a class, they are the instance (not singleton) methods. With no argument, or with an argument that is false, the instance methods in mod are returned, otherwise the methods in mod and mod’s superclasses are returned.
module A
def method1() end
end
class B
def method2() end
end
class C < B
def method3() end
end
A.instance_methods #=> [:method1]
B.instance_methods(false) #=> [:method2]
C.instance_methods(false) #=> [:method3]
C.instance_methods(true).length #=> 43
Solution 4 - Ruby on-Rails
You can do
current_user.methods
For better listing
puts "\n\current_user.methods : "+ current_user.methods.sort.join("\n").to_s+"\n\n"
Solution 5 - Ruby on-Rails
What about one of these?
object.methods.sort
Class.methods.sort
Solution 6 - Ruby on-Rails
If You are looking list of methods which respond by an instance (in your case @current_user). According to ruby documentation methods
> Returns a list of the names of public and protected methods of obj. > This will include all the methods accessible in obj's ancestors. If > the optional parameter is false, it returns an array of obj's > public and protected singleton methods, the array will not include > methods in modules included in obj.
@current_user.methods
@current_user.methods(false) #only public and protected singleton methods and also array will not include methods in modules included in @current_user class or parent of it.
Alternatively, You can also check that a method is callable on an object or not?.
@current_user.respond_to?:your_method_name
If you don't want parent class methods then just subtract the parent class methods from it.
@current_user.methods - @current_user.class.superclass.new.methods #methods that are available to @current_user instance.
Solution 7 - Ruby on-Rails
Suppose User has_many Posts:
u = User.first
u.posts.methods
u.posts.methods - Object.methods
Solution 8 - Ruby on-Rails
To expound upon @clyfe's answer. You can get a list of your instance methods using the following code (assuming that you have an Object Class named "Parser"):
Parser.new.methods - Object.new.methods