Fun with Bindings

fun_with_bindings.rb

class Blah
  def initialize
    @hello = 'world'
  end
end
blah = Blah.new
blah_binding = blah.instance_eval { binding }
ERB.new("<%= hello %>").result(blah_binding)
# Result:
# NameError: undefined local variable or method `hello' for #<Blah:0x00007fcb999d2990 @hello="world">
# Did you mean? @hello

# FIX 1:
class Blah
  attr_reader :hello
  
  def initialize
    @hello = 'world'
  end
end
blah = Blah.new
blah_binding = blah.instance_eval { binding }
ERB.new("<%= hello %>").result(blah_binding)
# => "world"

# Fix 2: (decorator pattern to capture a binding)
# OpenStruct has builtin accessors for instance varialbes that are created.
params = OpenStruct.new({hello: "world"})
params_binding = params.instance_eval { binding }
ERB.new("<%= hello %>").result(params_binding)
# => "world"