CODEWITHSUNDEEP
rubyruby-on-rails-3classmetaprogramming
user502052
user502052

Reputation: 15259

How to retrieve a class name?

I am using Ruby on Rails 3.0.7 and I would like to retrieve the class name, also if it is namespaced. For example, if I have a class named User::Profile::Manager I would retrieve the Manager string from that using some unknown to me Ruby or Ruby on Rails method and in a secure way.

BTW: What other "usefull" information that are "commonly" used can I get for the class?

Upvotes: 1

Views: 263

Answers (3)

Brett Bender
Brett Bender

Reputation: 19738

Some useful simple metaprogramming calls:

user = User::Profile::Manager.new(some_params)
user.class # => User::Profile::Manager
user.class.class # => Class
user.class.name # => "User::Profile::Manager"
user.class.name.class # => String

# respond_to? lets you know if you can call a method on an object or if the method you specify is undefined
user.respond_to?(:class) # => true
user.respond_to?(:authenticate!) # => Might be true depending on your authentication solution
user.respond_to?(:herpderp) # => false (unless you're the best programmer ever)

# class.ancestors is an array of the class names of the inheritance chain for an object
# In rails 3.1 it yields this for strings:
"string".class.ancestors.each{|anc| puts anc}

String
JSON::Ext::Generator::GeneratorMethods::String
Comparable
Object
PP::ObjectMixin
JSON::Ext::Generator::GeneratorMethods::Object
ActiveSupport::Dependencies::Loadable
Kernel
BasicObject

If you want the lowest-level class from User::Profile::Manager I'd probably do the following [using a regex for this seems like overkill to me ;)]:

user = User::Profile::Manager.new
class_as_string = user.class.name.split('::').last # => "Manager"
class_as_class = class_name.constantize # => Manager

Edit:

If you actually want to look through some more metaprogramming calls, check the docs for the Object and Module classes, and check out the google results for "Ruby Metaprogramming".

Upvotes: 3

Steve Wilhelm
Steve Wilhelm

Reputation: 6260

To expand on @JCorcuera's answer, some other useful information can be found with kind_of? and methods

class A
  class B
        def foo
        end
  end
end

myobject = A::B.new

p myobject.class
=> A::B

p myobject.kind_of? A::B
=> true

p myobject.methods
=> [:foo, :nil?, :===, :=~, ...

p myobject.methods.include? :foo
=> true

Upvotes: 1

JCorcuera
JCorcuera

Reputation: 6834

Have you tried class method:

class A
  class B
  end
end

myobject = A::B.new

myobject.class

=> A::B

Upvotes: 2

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