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---
datamapper: |-
DataMapper, the ruby object relational mapper
website: http://www.datamapper.org
git: git://github.com/datamapper/dm-core.git
mail: http://groups.google.com/group/datamapper
now: http://www.twitter.com/datamapper
irc://irc.freenode.net/datamapper
irc://irc.freenode.net/dm-hacking
before: http://irclogger.com/datamapper/
http://irclogger.com/dm-hacking/
bugs: http://datamapper.lighthouseapp.com/projects/20609-datamapper/
Setting up a Connection
DataMapper.setup(:default, "adapter://user:password@hostname/dbname")
supported adapters: mysql, sqlite3, postgres, sqlite3::memory:
additional adapters are in dm-more, (couchdb, rest, imap, file, saleforce...)
Creating a Model (with properties)
class Zoo
include DataMapper::Resource
property :id, Serial
end
Properties
property :id, Serial # auto-incrementing PK
property :name, String, :key => true # natural key
# you must specify >= 1 key, CPK support 100%
# available data-types
property :description, Text # (lazy by default)
property :created_at, DateTime
property :open, Boolean
property :admission, BigDecimal
# require dm-types for Csv, Enum, EpochTime, FilePath, Flag,
# IPAddress, URI, Yaml
Property Options (pass as hash)
:default, :nullable, :field (column name), :size, :length, :format,
:index, :unique_index, :ordinal, :auto_validation, :precision,
:scale, :accessor, :reader, :writer, :lazy
Finders
Zoo.get(PK_HERE)
Zoo.first({see_below})
Zoo.all({see_below})
Finder Options (pass as hash)
:conditions => ["property = ? and property = ?", 'value', 'value']
:conditions => {:property => 'value', ...}
:property => 'ZooNameHere'
# any non-standard key => value pair is assumed a condition if not
# otherwise recognized
:property.lte => 12.00 # <=
.gte # >=
.gt # >
.lt # <
.not # NOT =
.like # LIKE
.in # IN ()
'class.property' => 'value'
Class.relationship.property => 'value' # will automatically issue JOINS
Finder Gotcha
:order => [:created_at.desc, ...] # descending sort
.asc # ascending
Associations
has 1 # has_one
has n # has_many
belongs_to :things
has n, :more_things, :through => :things
has n, :things, :through => Resource # has_and_belongs_to_many
Association Options
(any Finder Options)
:model => 'ClassNameHere'
:order => [:property.desc]
:child_key => [:property, ...]
:through => :other_association
Validations (require 'dm-validations')
validates_present :title
validates_is_number :rating
validates_format :email, :as => :email_address
validates_length :summary, :in => (1..100)
validates_is_unique :slug
validates_with_method (do...end, :method_name)
Callbacks AKA "Hooks"
Object-level
before :method_name, (do...end, :another_method_name)
after :method_name, (do...end, :another_method_name)
Class-level
before_class_method :method_name, (do...end, :another_method_name)
after_class_method :method_name, (do...end, :another_method_name)
Callbacks Gotcha
Hooks act on 'self' and aren't passed an arguement
'self' for object-level hooks are the instance
'self' for class-level hooks are the class itself
Misc. Stuff & Gotchas
Single Table Inheritance
property :type, Discriminator # then inherit from this model
Paranoia
property :deleted_at, ParanoidDateTime
property :deleted, ParanoidBoolean
Multiple DB Connections
DataMapper.setup(:external, "adapter://username:password@hostname/dbname")
DataMapper.repository(:external) do...end
Association: has n, :things, :repository => repository(:external)
Finder: Thing.all(:repository => repository(:external))
DataMapper.setup(:colors_db, "sqlite3:path/to/colors.db")
class Color
include DataMapper::Resource
def self.default_repository_name
:colors_db
end
property :name, String
end
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