introspection/instance_variable_get_names.rb

tests/_examples/introspection/instance_variable_get_names.rb in the metorex repository.

class Greeter
  def initialize
    @greeting = "hello"
  end
end

class GreetingName
  def to_str
    "@greeting"
  end
end

greeter = Greeter.new

puts greeter.instance_variable_get("@greeting")
puts greeter.instance_variable_get(:@greeting)
puts greeter.instance_variable_get(GreetingName.new)
puts greeter.instance_variable_get(:@goodbye).inspect
puts nil.instance_variable_get(:@goodbye).inspect

["@", "@0", "@@greeting", "greeting"].each do |name|
  begin
    greeter.instance_variable_get(name)
  rescue NameError => error
    puts "#{error.class}: #{error.message}"
  end
end

begin
  greeter.instance_variable_get(10)
rescue TypeError => error
  puts "#{error.class}: #{error.message}"
end

Output:

hello
hello
hello
nil
nil
NameError: `@' is not allowed as an instance variable name
NameError: `@0' is not allowed as an instance variable name
NameError: `@@greeting' is not allowed as an instance variable name
NameError: `greeting' is not allowed as an instance variable name
TypeError: no implicit conversion of Integer into String