Core Data in Motion

A light-weight wrapper for Core Data that tries its hardest to be like ActiveRecord.

Features

Defining models

class Device < CDIM::Model
  # options can be :required => true/false (defaults to false) and/or :default => ...
  property :name, :string, :required => true
  property :ios_version, :float, :default => 6.0, :required => true
  property :udid, :string

  # an enum takes an additional option, an array of possible values
  # it can take a default as well, :default => :mac
  property :type, :enum, :values => [:iphone, :ipad, :mac], :required => true # transparently stored as an :int16
  
  # adds created_at & updated_at properties
  timestamp_properties
end

Creating records

iphone = Device.create(:name => 'iPhone', :type => :iphone, :udid => '...')
# or
ipad = Device.new
ipad.name = 'iPad'
ipad.type = :ipad
ipad.ios_version = 6.1
ipad.save

Updating records

iphone.update_attributes(:ios_version => 6.1)
# or
ipad.name = "Brendan's" + ipad.name
ipad.save

Finding records

devices = Device.all
# since Core Data has no concept of an id, first/last will try to use created_at to order items
# if that's not available, it will just return the first or last item from a fetch request, which has no guarentee of order
# (so specify a column or use timestamp_properties)
first_device = Device.first
# you can also specify your own column to order by for first or last
newest_ios = Device.last(:ios_version)

Destroying records

ipad.destroy

Has-one relationship

class Device
  has_one :owner
end

class Owner
  belongs_to :device
end

device = Device.create(:owner => Owner.new(:name => 'test'))
device.owner.name # 'test'

# assignment saves the object being assigned if the parent isn't a new record, but it doesn't save the association between the two
device.owner = nil
device.owner = Owner.new
Device.all.first.owner # still the old object

# create owner saves the association
device.create_owner(:name => 'new owner')

# build saves the parent object to have a nil relation
device.build_owner(:name => 'unsaved')
Device.all.first.owner # nil
device.save
Device.all.first.owner.name # 'unsaved'

Has-many relationship

class Manager
  has_many :employees
end
  
class Employee
  belongs_to :manager
end

manager = Manager.create
manager.employees.create # saves
manager.employees.build(:name => '..') # doesn't save
# saves the employee and relation right away unless manager.new_record?
# aliases: <<, :concat, can take an array as well
manager.employees.push(Employee.create)
manager.employees.clear # doesn't delete employees
first = manager.employees.first
manager.employees.destroy(first) # or delete
manager.employees.destroy_all # or delete_all

manager.employees << Device.create # raises an exception

Belongs-to relationship

Exactly the same as a has_one, but has_one/has_many relationships won't function without the presence of an inverse belongs_to relationship.

Data Types

• :int16/:integer16
• :int32/:integer32
• :int64/:integer64
• :double
• :float
• :string
• :bool/:boolean
• :binary
• :enum (pass in an array of values - this is not built in to Core Data)

Installation

Create a new RubyMotion project.

motion create myapp

Open it in your favorite editor, then go into your Rakefile and modify the top to look like the following:

# -*- coding: utf-8 -*-
$:.unshift("/Library/RubyMotion/lib")
require 'motion/project/template/ios'

begin
  require 'bundler'
  Bundler.require
rescue LoadError
end

require 'motion-support/concern'
require 'motion-support/core_ext/hash'
require 'motion-support/inflector'

Create a Gemfile and add the following lines:

source 'https://rubygems.org'
gem 'rake'
gem 'core-data-in-motion', :git => 'git://github.com/brendanjcaffrey/core-data-in-motion.git'
gem 'motion-support', :require => false

Run bundle install in Terminal to install Core Data In Motion.

To-Do

• Model.create
• Model.update_attributes
• Model.all
• Model.save
• Model.destroy/delete
• one-to-one relationships (has one, belongs to)
• one-to-many relationships (has_many)
• DSL for filtering and sorting (Model.where(...).limit(1), etc)
• apply DSL to has_many collections (model.children.where(..))
• schema migrations

Thanks to:

• http://swlkr.com/2013/01/02/an-intro-to-core-data-with-ruby-motion/
• http://github.com/alloy/MotionData/
• https://github.com/clearsightstudio/ProMotion (where I stole the Installation instructions from)