What you want to do is called dynamic dispatch. It’s very easy in Ruby, just use public_send:
method_name = 'foobar'
obj.public_send(method_name) if obj.respond_to? method_name
If the method is private/protected, use send instead, but prefer public_send.
This is a potential security risk if the value of method_name comes from the user. To prevent vulnerabilities, you should validate which methods can be actually called. For example:
if obj.respond_to?(method_name) && %w[foo bar].include?(method_name)
obj.send(method_name)
end
