Marshal.dump fails on extended OpenStruct

ruby-talk
1

If I subclass OpenStruct and extend the subclass, I cannot
Marshal.dump it. This is apparently because ostruct.rb has its own
custom marshal_dump / marshal_load that only cares about what's in
@table:

  def marshal_dump
    @table
  end
  def marshal_load(x)
    @table = x
    @table.each_key{|key| new_ostruct_member(key)}
  end

Is there no way to fix this in ostruct.rb to allow my 'bad' example
below to work?

require 'pp'
require 'ostruct'

case ARGV.first
    when /bad/i,nil
        class C < OpenStruct
            def initialize
                super()
                @var=123
            end
        end
    when /good/i
        class C
            def initialize
                @struct=OpenStruct.new
                @var=123
            end

            def method_missing method,*args,&block
                @struct.send method,*args,&block
            end
        end
end

c=C.new
c.a=:a
pp c
puts 'c.a=%s ' % c.a
puts 'c var=%s' % c.instance_variable_get('@var')
x=Marshal.load(Marshal.dump(c))

pp x
puts 'x.a=%s ' % x.a
puts 'x var=%s' % x.instance_variable_get('@var')

2

synergism wrote:

If I subclass OpenStruct and extend the subclass, I cannot
Marshal.dump it. This is apparently because ostruct.rb has its own
custom marshal_dump / marshal_load that only cares about what's in
@table:

  def marshal_dump
    @table
  end
  def marshal_load(x)
    @table = x
    @table.each_key{|key| new_ostruct_member(key)}
  end

Is there no way to fix this in ostruct.rb to allow my 'bad' example
below to work?

require 'pp'
require 'ostruct'

case ARGV.first
    when /bad/i,nil
        class C < OpenStruct
            def initialize
                super()
                @var=123
            end
        end
    when /good/i
        class C
            def initialize
                @struct=OpenStruct.new
                @var=123
            end

            def method_missing method,*args,&block
                @struct.send method,*args,&block
            end
        end
end

c=C.new
c.a=:a
pp c
puts 'c.a=%s ' % c.a
puts 'c var=%s' % c.instance_variable_get('@var')
x=Marshal.load(Marshal.dump(c))

pp x
puts 'x.a=%s ' % x.a
puts 'x var=%s' % x.instance_variable_get('@var')

You could just write new marshal_dump and marshal_load methods:

require 'ostruct'
require 'pp'
class C < OpenStruct

  def initialize *args super @var = 123 end

  def marshal_dump
    [@table, Hash[self.instance_variables.map { |v| [v, self.instance_variable_get("#{v}")] }]]
  end

  def marshal_load x
    @table = x[0]
    @table.each_key{|key| new_ostruct_member(key)}
    x[1].each do |k,v|
      self.instance_variable_set("#{k}", v) unless k.to_sym == :table
    end end end

c=C.new
c.a=:a
pp c
puts 'c.a=%s ' % c.a
puts 'c var=%s' % c.instance_variable_get('@var')
x=Marshal.load(Marshal.dump(c))

pp x
puts 'x.a=%s ' % x.a
puts 'x var=%s' % x.instance_variable_get('@var')

-Justin

3

Justin Collins wrote:

synergism wrote:

If I subclass OpenStruct and extend the subclass, I cannot
Marshal.dump it. This is apparently because ostruct.rb has its own
custom marshal_dump / marshal_load that only cares about what's in
@table:

  def marshal_dump
    @table
  end
  def marshal_load(x)
    @table = x
    @table.each_key{|key| new_ostruct_member(key)}
  end

Is there no way to fix this in ostruct.rb to allow my 'bad' example
below to work?

require 'pp'
require 'ostruct'

case ARGV.first
    when /bad/i,nil
        class C < OpenStruct
            def initialize
                super()
                @var=123
            end
        end
    when /good/i
        class C
            def initialize
                @struct=OpenStruct.new
                @var=123
            end

            def method_missing method,*args,&block
                @struct.send method,*args,&block
            end
        end
end

c=C.new
c.a=:a
pp c
puts 'c.a=%s ' % c.a
puts 'c var=%s' % c.instance_variable_get('@var')
x=Marshal.load(Marshal.dump(c))

pp x
puts 'x.a=%s ' % x.a
puts 'x var=%s' % x.instance_variable_get('@var')

Let me try that again:

require 'ostruct'
require 'pp'

class C < OpenStruct

  def initialize *args
    super
   @var = 123
  end def marshal_dump
    [@table, Hash[self.instance_variables.map { |v| [v, self.instance_variable_get("#{v}")] }]]
  end def marshal_load x
    @table = x[0]
    @table.each_key{|key| new_ostruct_member(key)}
    x[1].each do |k,v|
      self.instance_variable_set("#{k}", v) unless k.to_sym == :table
    end
  end
end

c=C.new
c.a=:a
pp c
puts 'c.a=%s ' % c.a
puts 'c var=%s' % c.instance_variable_get('@var')
x=Marshal.load(Marshal.dump(c))

pp x
puts 'x.a=%s ' % x.a
puts 'x var=%s' % x.instance_variable_get('@var')

4

Thanks. I considered that, but the bigger issue is that this makes
using DRb in any application of non-trivial complexity quite painful,
as we now need to mess with the implementation details of every
serialized object. I was just hoping something more transparent could
be done with ostruct to make things better.

Incidentally, I continued with the delegation model I used in my
example and found that this wasn't where the trouble ended. I had to
also eliminate an un-dumpable proc I had used to auto-initialize a
Hash of Hashes (to make an empty hash be the default value so that
references would not raise an exception on uninitialized keys) i.e.

class AutoHash < Hash
    def key
        _=fetch(key) rescue _=store(key,{})

···

On Feb 17, 4:32 pm, Justin Collins <justincoll...@ucla.edu> wrote:

You could just write new marshal_dump and marshal_load methods:

        _
    end
end

class C
    def initialize
        # ...
        @attributes=AutoHash.new
    end
end

instead of:

        # ...
        @attributes=Hash.new{|hash,key| hash[key]={}}

It seems programming with DRb is fraught with difficulties like
these. I wish we had something easier to use, as otherwise DRb is
exactly what we need for this application.

Ben

5

Justin Collins wrote:

Justin Collins wrote:

synergism wrote:

If I subclass OpenStruct and extend the subclass, I cannot
Marshal.dump it. This is apparently because ostruct.rb has its own
custom marshal_dump / marshal_load that only cares about what's in
@table:

  def marshal_dump
    @table
  end
  def marshal_load(x)
    @table = x
    @table.each_key{|key| new_ostruct_member(key)}
  end

Is there no way to fix this in ostruct.rb to allow my 'bad' example
below to work?

require 'pp'
require 'ostruct'

case ARGV.first
    when /bad/i,nil
        class C < OpenStruct
            def initialize
                super()
                @var=123
            end
        end
    when /good/i
        class C
            def initialize
                @struct=OpenStruct.new
                @var=123
            end

            def method_missing method,*args,&block
                @struct.send method,*args,&block
            end
        end
end

c=C.new
c.a=:a
pp c
puts 'c.a=%s ' % c.a
puts 'c var=%s' % c.instance_variable_get('@var')
x=Marshal.load(Marshal.dump(c))

pp x
puts 'x.a=%s ' % x.a
puts 'x var=%s' % x.instance_variable_get('@var')

Let me try that again:

require 'ostruct'
require 'pp'

class C < OpenStruct

def initialize *args
   super
  @var = 123
end def marshal_dump
   [@table, Hash[self.instance_variables.map { |v| [v, self.instance_variable_get("#{v}")] }]]
end def marshal_load x
   @table = x[0]
   @table.each_key{|key| new_ostruct_member(key)}
   x[1].each do |k,v|
     self.instance_variable_set("#{k}", v) unless k.to_sym == :table
   end
end
end

c=C.new
c.a=:a
pp c
puts 'c.a=%s ' % c.a
puts 'c var=%s' % c.instance_variable_get('@var')
x=Marshal.load(Marshal.dump(c))

pp x
puts 'x.a=%s ' % x.a
puts 'x var=%s' % x.instance_variable_get('@var')

I give up. I don't know why the formatting is all weird.

-Justin