Can't change the value of self

ruby-talk
1

Ok ... I've googled this error and I see stome explanations about usnig destructive methods ...

I don't get it.

Consider

- - - -
class UD_Config
  attr_accessor :container_list
  attr_accessor :screen_x, :screen_y, :screen_width, :screen_height
  
  @@config_filename = 'config.yml'
  
  def initialize
    debugger
    if File.exists? @@config_filename
      config_yaml_str = IO.read(@@config_filename)
      self = YAML::load( config_yaml_str ) # This line seems to be the problem
    else
      set_defaults
    end
  end
  
  def write_me
    yaml_obj = YAML::dump( self )
    File.open(filename,"w") { |f| f << yaml_obj }
  end
  
private
  # call this if there is no config file
  def set_defaults
    screen_x, screen_y, screen_width, screen_height = 30, 30, 600, 500
    
    @container_list =
      %w(
        c:\abc\def.udd
        d:\def\ghi.udd
        f:\\ghi\jkl.udd
      )
  end
end

- - - -

I have been taught that "an object should take care of itself" ... what's the right way to do what I want?

2

Ralph Shnelvar wrote:

I have been taught that "an object should take care of itself" ...

It can take care of itself, it can't turn into someone else :slight_smile:

If YAML.load is returning an instance of class UD_Config directly, then
just return that to the user. Make a class method, so they call

   res = UD_Config.load(...)

instead of

   res = UD_Config.new(...)

Otherwise, YAML.load is returning some other object - possibly a Hash -
with which you wish to initialize your new UD_Config object. So you need
to copy values out of that object into your object's instance variables.

If YAML.load gives an object with instance variables, you can copy them
in a loop: look at 'instance_variables' and 'instance_variable_get' /
'instance_variable_set'

···

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