CODEWITHSUNDEEP
rubylearn-ruby-the-hard-way
AlaskaStack
AlaskaStack

Reputation: 57

Ruby Exercise 18 undefined method although i defined the methods

Hi i get the error "undefined method" in the exercise 18 although i did it like its written. 

class Exercise18_NamesVariablesCodeFunctions

# this one is like your scripts with ARGV
 def print_two(*args)
  arg1, arg2 = args
  puts "arg1: #{arg1}, arg2: #{arg2}"
 end

# ok, that *args is actually pointless, we can just do this
 def print_two_again(arg1, arg2)
  puts "arg1: #{arg1}, arg2: #{arg2}"
 end

# this just takes one argument
 def print_one(arg1)
  puts "arg1: #{arg1}"
 end

# this one takes no arguments
 def print_none()
  puts "I got nothin'."
 end


 print_two("Zed","Shaw")
 print_two_again("Zed","Shaw")
 print_one("First!")
 print_none()

end

Here's my error:

exercise18_names_variables_code_functions.rb:25:in `<class:Exercise18_NamesVariablesCodeFunctions>': undefined method `print_two' for Exercise18_NamesVariablesCodeFunctions:Class (NoMethodError)
Did you mean?  print
    from exercise18_names_variables_code_functions.rb:1:in `<top (required)>'
    from -e:1:in `load'
    from -e:1:in `<main>'

I dont understand this error. I defined all the method. When i add self. to all methods it works.

Upvotes: 1

Views: 73

Answers (2)

Santosh Sharma
Santosh Sharma

Reputation: 2248

Try Following.

class Exercise18_NamesVariablesCodeFunctions

# this one is like your scripts with ARGV
 def print_two(*args)
  arg1, arg2 = args
  puts "arg1: #{arg1}, arg2: #{arg2}"
 end

# ok, that *args is actually pointless, we can just do this
 def print_two_again(arg1, arg2)
  puts "arg1: #{arg1}, arg2: #{arg2}"
 end

# this just takes one argument
 def print_one(arg1)
  puts "arg1: #{arg1}"
 end

# this one takes no arguments
 def print_none()
  puts "I got nothin'."
 end

a = Exercise18_NamesVariablesCodeFunctions.new

 a.print_two("Zed","Shaw")
 a.print_two_again("Zed","Shaw")
 a.print_one("First!")
 a.print_none()

end

Upvotes: 0

davidhu
davidhu

Reputation: 10472

The reason is any method call from inside the class is calling the class methods, whereas all the method you defined are instance methods.

As your code is currently written, you can call those methods after defining an instance of the class.

exercises = Exercise18_NamesVariablesCodeFunctions.new

exercises.print_two("Zed","Shaw") #=> "arg1: Zed, arg2: Shaw"

Exercises is an instance of the class itself, and, therefore, have access to the instance methods of that class.

If you want to call the methods as you have currently, you need to change those methods to class methods, but simply adding self. before the name of each function

 def self.print_two(*args)
  arg1, arg2 = args
  puts "arg1: #{arg1}, arg2: #{arg2}"
 end

Now, you will be able to call that method from inside the class.

You can also wrap all of your class methods in a container.

class Test
  class << self
    def first_method
    end

    def second_method
    end
  end
end

Now, any method inside the class << self is a class method.

Upvotes: 3

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