From: Dejan Dimic <dejan.dimic@...>
Date: 2008-09-30T05:34:50+09:00
Subject: Re: Accessing a YAML loaded object without the object's definition?

On Sep 29, 8:05 pm, Steve Litt <sl...@troubleshooters.com> wrote:
> Hi all,
>
> In Ruby, I have a fairly complex nested object structure that I serialize to a
> yaml file. Then, in another program, I read it into a varaible like this:
>
> obj = YAML::load_file("myfile.yaml");
>
> I can see all objects and names in obj within irb, but I can't access them
> individually. For instance, in the original native that created the yaml,
> there's this:
>
> obj.customer.city
>
> You cannot access that from the object read in with load_file. It creates an
> error condition.
>
> What DOES work is:
>
> obj = Purchase.new(nil, nil)
> obj = YAML::load_file("myfile.yaml");
>
> puts obj.customer.city
>
> That prints "Apopka".
>
> A sample program is at the bottom of this email. As long as the classes are
> defined in the program, they can be accessed. But if an object is created via
> YAML::load_file(), I'm not able to access its data members.
>
> Is there any way I can do it without including the class definition in the
> code?
>
> Thanks
>
> SteveT
>
> Steve Litt
> Recession Relief Packagehttp://www.recession-relief.US
>
> ############ SAMPLE PROGRAM ###################
> #!/usr/bin/ruby -w
>
> require "yaml"
>
> class Address
>         attr_accessor :street, :city, :state, :zip
>         def initialize(street, city, state, zip)
>                 @street = street
>                 @city = city
>                 @state = state
>                 @zip=zip
>         end
> end
>
> class Customer
>         attr_accessor :fname, :lname, :address
>         def initialize( fname, lname, address)
>                 @fname = fname
>                 @lname = lname
>                 @address = address
>         end
> end
>
> class Item
>         attr_accessor :quantity, :priceper, :name
>         def initialize(name, quantity, priceper)
>                 @name = name
>                 @quantity = quantity
>                 @priceper = priceper
>         end
> end
>
> class Purchase
>         attr_accessor :customer
>         attr_reader :amount
>         attr_accessor :date
>         attr_reader :items
>
>         def initialize(customer, date)
>                 @customer = customer
>                 @amount = amount
>                 @date = date
>                 @items = Array.new()
>         end
>         def additem(item)
>                 @items.push(item)
>         end
>         def update_amount()
>                 @amount = 0
>                 @items.each do
>                         |item|
>                         @amount += (item.quantity.to_f * item.priceper.to_f)
>                 end
>         end
> end
>
> #### MAIN ROUTINE
> #### Load objects
> address = Address.new(["121 Main Street", "Suite
> 201"], "Apopka", "FL", "33333");
>
> customer = Customer.new("Steve", "Litt", address)
>
> purchase = Purchase.new(customer, "3/3/2033")
> purchase.additem(Item.new("Widget", 1, 1.00));
> purchase.additem(Item.new("Gadget", 2, 2.00));
> purchase.additem(Item.new("Left handed smoke bender", 3, 3.00));
> purchase.update_amount()
>
> #### Write out YAML to junk.yaml
> ouf = File.new("./junk.yaml", "w");
> ouf.write(YAML::dump(purchase))
> ouf.close()
>
> #### WRITE REPORT
> #### Read YAML file and load into Purchase object p
> p=Purchase.new(nil, nil)
> p=YAML::load_file("./junk.yaml");
>
> #### Date and total
> printf "Purchase on %s, total cost $%0.2f\n", p.date, p.amount
>
> #### Customer data
> printf "\nCUSTOMER DATA:\n"
> printf "%s %s\n", p.customer.fname, p.customer.lname
> p.customer.address.street.each {|i| puts i}
> printf "%s, %s, %s\n", p.customer.address.city, p.customer.address.state,
> p.customer.address.zip
>
> #### Items
> printf "\nITEMS PURCHASED\n"
> printf "%30s %10s %10s %10s\n", "ITEM NAME", "QUANTITY", "@", "TOTAL"
> p.items.each do
>         |item|
>         printf "%30s %10d %10.2f %10.2f\n", item.name, item.quantity, item.priceper,
> item.quantity * item.priceper
>
> end
> printf "%30s %10s %10s %10s\n", " ", " ", " ", "----------"
> printf "%30s %10s %10s %10.2f\n", "TOTAL", " ", " ", p.amount
>
> ############ END OF SAMPLE PROGRAM ###################

take look at: http://yaml4r.sourceforge.net/doc/page/type_families.htm