ixtlan-datamapper

Ixtlan DataMapper

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it adds optimistic persistence support to DataMapper and ActveRecord using the updated_at property/attribute which is automatically updated on any change of the model (for datamapper you need dm-timestamps for that). to load a model use optimistic_get/optimistic_get!/optimistic_find respectively where the first argument is the last updated_at value which the client has. if the client data is uptodate then the optimistic_XYZ method will return the database entity otherwise raise an exception or return nil respectively.

optimistic/conditional get

just include require 'ixtlan/datamapper/optimistic' and have model like:

class User
  include DataMapper::Resource

  property :id, Serial
  property :name, String

  timestamps :at
end

you need the timestamps to get it to work since the updated_at property will be used to determine if the object is stale or not.

now you get the object in an optimistic manner

User.optimistic_get!( updated_at, id )
User.optimistic_get( updated_at, id )

if will raise an Ixtlan::DataMapper::StaleObjectException in case the object with the given id exists but does carry a different updated_at timestamp. otherwise the optimistic_get and optimistic_get! behave the same as get and get!.

now you get the object in an conditional manner

User.conditinal_get!( updated_at, id )
User.conditional_get( updated_at, id )

it the User when the updated_at does not match. when it matches it returns false. in case the id does not exist, it will return either nil of DataMapper::ObjectNotFoundError. this allows constructs like

if u = User.conditinal_get!( request.last_modified, id )
  response.last_modified = u.updated_at
  response.write ....
else
  # in case request.last_modified was nil
  response.last_modified = u.updated_at	  
end

Ixtlan::DataMapper::Immutable

class Group
  include DataMapper::Resource
  include Ixtlan::DataMapper::Immutable

  property :id, Serial
  property :name, String
end

you can create and delete those object but any attempt to change it the name ends in validation error.

require 'ixtlan/datamapper/use_utc'

just convenient file to setup datamapper to use UTC timestamps

Ixtlan::DataMapper:Collection

the collection is virtus object which helps to transport collections of DataMapper objects around. it has the total_count and an offset along an accessor for the list. the contructor deals with offset and limit on the datamapper query.

class UserCollection < Ixtlan::DataMapper::Collection
  attribute :users, Array[User]
  def data=( d )
    self.users = d
  end
end

this

UserCollection.new( User.all( :name.like => 'a%' ), 20, 10 )

will return 10 users starting with 'a' starting with 20th user from all possible users (with 'a').

Contributing

1. Fork it
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Added some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create new Pull Request

meta-fu

enjoy :)