Getting a User Input In Ruby

Question

Hi, I have a quick question in Ruby

Lets say I ask the user to enter a name ( for a new class that i want to create)

my code is:

puts "enter the name for a new class that you want to create"
nameofclass = gets.chomp
nameofclass = Class.new

Why does this not work?

Also, I want to ask the user to enter the name of a method that i want to add to that class

my code is:

puts "enter the name for a new method that you want to add to that class"
nameofmethod = gets.chomp

nameofclass.class_eval do
    def nameofmethod
      p "whatever"
    end
end

This does not work either

-Can anyone help me please, Thank you

Answer 1

The following code:

nameofclass = gets.chomp
nameofclass = Class.new

Is interpreted by the machine as:

Call the function "gets.chomp"
Assign the output of this call to a new variable, named "nameofclass"
Call the function "Class.new"
Assign the output of this call to the variable "nameofclass"

As you can see, if you follow the above, there is one variable, which gets assigned to twice. When the second assignment happens, the first is lost.

What you're trying to do, is presumably to create a new class and name it the same as the result of gets.chomp. To do this, you could use eval:

nameofclass = gets.chomp
code = "#{nameofclass} = Class.new"
eval code

There are other ways too, this being Ruby, but eval is probably the easiest to understand.

Answer 2

I like troelskn's answer for its explanation of what's happening quit a bit.

To avoid using the very dangerous eval, try this:

Object.const_set nameofclass, Class.new