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gem "mongo", "1.0"
gem "bson_ext", "1.0"
gem "mongo_ext", "0.19.3"
gem "mongo_mapper", "0.7.5"
require 'mongo_mapper'
MongoMapper.database = 'shopping'
class List
include MongoMapper::Document
key :name, String
many :items
def destroy_item!(item_id)
items.delete_if do |i| == item_id
class Item
include MongoMapper::EmbeddedDocument
key :price, Float
# Setup prop
list ={:name => 'groceries'})
cheap_item ={:price => 5.00})
expensive_item ={:price => 3.00})
list.items = [] << cheap_item << expensive_item
puts "Is item count 2: #{list.items.count == 2}"
# Deletion by object id directly works fine
puts "Is item count 1: #{list.items.count == 1}"
# However if we send the object id as a string we get into trouble
puts "Is item count 0: #{list.items.count == 0}"
# This matters a fair bit when you are using restful resources over the web
# to handle the removal and updating of persisted objects.
# For example using sinatra we can handle a post to the
# resource /items/:list_id/:item_id/delete
# Rack then makes :item_id available in our params hash as a string,
# and from there you can get easily caught out as in the example above.
# I don't mind working around this with my model code - it might not even be a bug
# in mongo mapper bug perse. Just a bit assyemtric considering we can successfully
# query for an object with find with the id represented as a string. The same
# should apply to equivalence tests on object ids.
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