can I use a variable name in the place of an object name in ruby

Question

Recently, I just wrote a simple game in Ruby. I needed the user to input a object's name which I created earlier.

When I give the variable name in the place of object's name, ruby thinks it is another string and outputs that

there is no such method(no method error)

How can I solve this?

class game
  #somecode
  def weapon_power
    @power
  end
end

object = game.new
x = gets #user inputs object
puts x.weapon_power

score 1 · Answer 1 · answered Feb 16 '18 at 17:52

You set the variable x to the return value of the gets method. This method always returns a String object.

Now, in your code, you are trying to call the weapon_power method on this String object which naturally fails since Strings don't have such a method.

I'm not exactly sure what you want to achieve here in the first place though, but you can call the weapon_power method on your object like this:

object.weapon_power

As a final note, please be aware that in Ruby, class names (like your game always have to start with a capital letter. It thus has to be spelled Game instead. With your exact code, you would have received a SyntaxError.

score 1 · Answer 2 · answered Feb 16 '18 at 18:27

I think you are asking how to instantiate your Game object via it's name in a string.

x = gets
clazz = Object.const_get(x)
obj = clazz.new

If the class is already instantiated you'll have to do more work. Maybe something like this

gameInstance = Game.new

x = gets
case x
when 'Game'
    puts gameInstance.weapon_power
else
    puts 'Unknown input'
end

Possible duplicate of: How do I create a class instance from a string name in ruby?

score 0 · Answer 3 · answered Feb 16 '18 at 17:51

I'm not 100% I undestand what you want - looks like using the user input to identify a variable, correct?

If so, an easy way would be through a Hash:

object = game.new

objects = { "object" => object }
x = gets #user inputs object
puts objects[x].weapon_power # retrieve object named "object" and call the weapon-power on it

Benefit is that this would work with several objects in the Hash if needed.

can I use a variable name in the place of an object name in ruby

3 Answers3