CODEWITHSUNDEEP
rubyclass
monsur
monsur

Reputation: 601

I can not understand "uninitialized constant" in ruby

I have two files in folder pc under my home directory.

First file:

 class A
  class << self
   protected
    def foo
      puts "In foo"
     end
   end
 end

Second file:

  class B < A
   def bar
    self.class.class_eval { foo }
   end
  end

 B.new.bar

My problem is when I run the second file I get the following error:

  second.rb:1:in `<main>': uninitialized constant A (NameError)

Why is that?

Upvotes: 0

Views: 996

Answers (3)

PericlesTheo
PericlesTheo

Reputation: 2469

Try require_relative 'class_a' or require class_a.

Note that the file's extension is not included.

Upvotes: 1

zeantsoi
zeantsoi

Reputation: 26193

This should work, assuming it's all in the same file. If not, you'll need to require the first file into the next:

# class_b.rb
require 'class_a.rb'

class B < A
  def bar
    self.class.class_eval { foo }
  end
end

B.new.bar
#=> "In foo"

UPDATE:

In order to require the file, you may need to cite the path of the file relative to your current directory. For instance, if class_a.rb is located in ~/home and you're running irb (or class_b.rb is in ~/home), then you'd include class_a.rb by citing its relative path as follows:

require './class_a'

Upvotes: 1

Simone Carletti
Simone Carletti

Reputation: 176352

B.new.bar
# => In foo

just works fine in my console. I guess you probably forgot to require the file containing A from the file B.

In file B use

require 'a'

(assuming the file containing A is called a.rb).

I read the various comments, and just to avoid confusion, here's the full content of the two files.

class_a.rb

class A
  class << self
    protected
    def foo
      puts "In foo"
    end
  end
end

class_b.rb

require_relative 'class_a'

class B < A
  def bar
   self.class.class_eval { foo }
  end
end

puts B.new.bar

And here's how to execute them from the console

$ ruby class_b.rb 
In foo

Of course, you should execute the file class_b.rb, not class_a.rb or you will not see any result.

Upvotes: 2

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