CoreData relationship sample (w/ preliminary iCloud support)

NOTE: Preliminary iCloud support has just been added.

This sample demonstrate how to use CoreData in RubyMotion without using XCode and XCode data models:

• relationships and attributes are supported
• default, optional, transient and indexed properties are supported for attributes
• optional, transient, indexed, ordered, min, max and delete-rule properties are supported for relationships
• attributes and relationships are specified declaratively and on a per object basis
• store.rb is mostly independent from the objects
• some CoreData helper/extension classes are provided in lib/
• both table views with and without sections are demonstrated

Creating a Game class

A Game is identified by a name, occurs within a given year and has a timestamp. A game also has several players:

class Game < NSManagedObject

  @attributes = [
	{:name => 'name',      :type => NSStringAttributeType},
	{:name => 'timestamp', :type => NSDateAttributeType},
	{:name => 'year',      :type => NSInteger16AttributeType},
  ]
  
  @relationships = [
	{:name => 'players', :destination => 'Player', :inverse => 'game'},
  ]

In addition, games are grouped by year, sorted by timestamp and searched by name:

class Game < NSManagedObject
  @sortKeys = ['timestamp']
  @sectionKey = 'year'
  @searchKey = 'name'

Options are available if you wish to provide defaults for attributes, or if attributes are not optional, transient or indexed:

class Game < NSManagedObject
  @attributes = [
	{:name => 'name', :type => NSStringAttributeType, :default => '', :optional => false, :transient => false, :indexed => false},
	{:name => 'timestamp', :type => NSDateAttributeType, :default => nil, :optional => false, :transient => false, :indexed => false},
	{:name => 'year', :type => NSInteger16AttributeType, :default => 0, :optional => false, :transient => false, :indexed => false},
  ]

The same holds for relationships:

class Game < NSManagedObject
  @relationships = [
	{:name => 'players', :destination => 'Player', :inverse => 'game', :json => 'players', :optional => true, :transient => false, :indexed => false, :ordered => true, :min => 0, :max => NSIntegerMax, :del => NSCascadeDeleteRule},
  ]

Creating a Store

A Store is created simply by indicating the name of the NSManagedObject classes; in our example Game and Player:

class Store
  DB = 'store.sqlite'
  ManagedObjectClasses = [Game, Player]

Accessing a Game

The fetchedResultsController for a game is accessed as follows. You need to first reset the cache for the fetchedResultsController:

Game.reset
Game.controller

If you want instead to filter objects using a given search string, use:

Game.reset 
Game.searchController('name1')

Here's how to access the section name, the number of objects in the section and an object at the given indexpath:

Game.controller.sections[section].name
Game.controller.sections[section].numberOfObjects
Game.controller.objectAtIndexPath(indexPath).name

Or it you want to use the search controller instead:

Game.searchController('name1').sections[section].name
Game.searchController('name1').sections[section].numberOfObjects
Game.searchController('name1').objectAtIndexPath(indexPath).name

Editing a Game

A game can be edited easily; a dedicated UITableView will be created automatically to let the user edit the game's fields:

@gameController ||= UITableViewControllerForNSManagedObject.alloc.initWithStyle(UITableViewStyleGrouped)
@navGameController ||= UINavigationControllerDoneCancel.withRootViewController(@gameController, target:self, done:'doneEditing', cancel:'cancelEditing')

@gameController.object = game
@gameController.is_update = true
navigationController.presentModalViewController(@navGameController, animated:true)

From Game to JSON (and vice-versa)

A Game can then easily be output in JSON:

game.to_json

A Game can be easily created from a JSON string:

json = '{
    "timestamp": "5/11/2012",
    "year": 2012,
	"name": "game1"
}'

Game.add do |game|
  game.from_json(json)
end