Ruby symbol to class

user_144697 0
Viewed 19465

Is there a way in Ruby to take a symbol or string and turn it into a class of the same name?

For instance, if I have a class such as

class Bob
  def talk
     puts "Hi, I'm bob"
  end
end

And a method I have somewhere else in the code is passed a symbol :bob, can I in some way turn that into the class Bob? Maybe something like

b = :Bob.new
b.talk

Or is there a way to do something similar to this?

transform symbols class ruby
7 Answers

There are many ways to do this. Your lack of context makes it impossible to elect a "best" way. Here's a few ayways.

Kernel.const_get(:Bob)

eval(:Bob.to_s)

Kernel.const_get(:bob.to_s.capitalize)
user_260510

Rails

For use with Rails only.

With a string:

"Module".constantize #=> Module
"Class".constantize #=> Class

With a symbol:

:module.to_s.classify.constantize #=> Module
:open_struct.to_s.classify.constantize #=> OpenStruct

If you are dealing with a multi-word symbol, then you'll want to add #classify to the chain to properly handle the capitalization of all the parts of the constant.

http://api.rubyonrails.org/classes/ActiveSupport/Inflector.html#method-i-constantize

user_806530

NameSpace.const_get(classname) will return the class object (assuming that classname contains the name of a class - if it contains the name of a constant that is not a class, it will return the value of that constant). The toplevel namespace is Object, so you can do Object.const_get(:Bob).new

user_1493920 
class Bob
end

def create(name)
  return eval("#{name}.new")
end

b = create(:Bob)
puts b.class
user_1055360
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