The Dangers of Ruby 'for' and metaprogramming

for_vs_each.rb

THINGS = %w{ foo bar baz }

class EachThing
  THINGS.each do |thing|
    define_method(thing) { thing }
  end
end

class ForThing
  for thing in THINGS do
    define_method(thing) { thing }
  end
end

puts "============EACH==========="
puts "foo: #{ EachThing.new.foo }"
puts "bar: #{ EachThing.new.bar }"
puts "baz: #{ EachThing.new.baz }"


puts "============FOR============"
puts "foo: #{ ForThing.new.foo }"
puts "bar: #{ ForThing.new.bar }"
puts "baz: #{ ForThing.new.baz }"

results

============EACH===========
foo: foo
bar: bar
baz: baz
============FOR============
foo: baz
bar: baz
baz: baz