Change dangerous use of OpenStruct

[u0078867]

The following:

require 'ostruct'

class Entity < OpenStruct

  def initialize
    super
    @context = "instance var"
  end

end

entity = Entity.new

pp entity.context
pp entity.instance_variable_get("@context")

entity.context = "custom attribute"

pp entity.context
pp entity.instance_variable_get("@context")

will output:

nil
"instance var"
"custom attribute"
"instance var"

However, adding this lines:

require 'ostruct'

class Entity < OpenStruct

  attr_accessor :context   # added

  def initialize
    super
    @context = "instance var"
  end

end

entity = Entity.new

pp entity.context
pp entity.instance_variable_get("@context")

entity.context = "custom attribute"

pp entity.context
pp entity.instance_variable_get("@context")

will output:

"instance var"
"instance var"
"custom attribute"
"custom attribute"

There is a collision between instance variables and OpenStruct custom attributes, of course.

I propose to change to:

class Entity

  attr_accessor :context

  def initialize
    @attributes = OpenStruct.new
    @context = "instance var"
  end

end

@mehmetc do you agree?

[mehmetc]

I agree. But also understand what is going on.
@context here is an instance variable. These are by default not accessible from outside of the instance.
When you do entity.context = "custom attribute" then the logic within OpenStruct will create the attr_accessor for you and overwrite the existing attribute.

[mehmetc]

That being said we should reevaluate OpenStruct and also how we create the ORM in Ruby. It still doesn't feel correct. You can for example create extra attributes that will not validate. For the ORM part we are doing a lot of work for a problem that is already solved by ActiveRecord, ...
Ruby also has the newer Data class here is a benchmarking and OpenStruct looks like a bad choice.