Have you tried to use CoreData in RubyMotion, only to get lost in the quagmire of simplistic or confusing examples, DSL's and gems? Have you been asking yourself these questions: Do I have to use XCode to create a CoreData model?; How do relationships work in code work anyway?; How do I pre-load data into my CoreData store?; What is an NSFetchedResultsController, and why do I need one? We'll delve into each of these questions, and review the surprisingly simple, elegant solutions that RubyMotion can provide.

1. Core Data in Motion
NSScotland 2013 - Oct 19/20
Monday, 21 October, 13

2. Who?
• Lori M Olson
• @wndxlori
• on Github too
• and ADN
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3. i Develop
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Ruby (mostly)
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Rails
iOS (RubyMotion)
JRuby
Javascript (some)
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jQuery
Maps/Charts
Javascript Testing

4. i Teach
• Ruby on Rails for Real Developers
(RoR4Real)
• Rails for iOS Developers (Rails4iOS)
• Ladies Learning Code - Ruby Introduction
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5. i Speak
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2013
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RubyConf AU, NSScotland
2012
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Confoo, RailsConf, Aloha RubyConf
2011
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jQueryConf, Madison Ruby
2010
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Conferencia Rails
2009
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RailsConf

6. Warning:
LOTS of code
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7. The Story
• To rewrite a (mobile) web application
(WIMBY) as an iOS application
• Using RubyMotion
• WIMBY = Wells In My Back Yard
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8. The Challenges
• LOTS of data
• On a Map
• In a list (table view)
• Filtering by location
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9. Oh, not much data
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10. RubyMotion gems/DSL’s
• Nitron
• MotionDataWrapper
• MotionModel
• MotionMigrate
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11. iOS Basics
• Ray Wenderlich!
• http://www.raywenderlich.com/934/coredata-tutorial-for-ios-getting-started
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12. Problems
• RubyMotion gems/DSL’s hide a lot
• Straight iOS Objective-C development
relies on Xcode magic (hides a lot)
• Complex data is complex
• Large data is large
• What do I do when I reach the limitations
of these solutions?
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13. The Real Problem
• Sometimes you just need to understand
how to solve problems at the most basic
API code level, and the abstractions (and
magic) just get in the way
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14. It’s not as scary as it looks
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15. What?
• Models (entities) in code
• Relationships in code
• Loading data
• Optimization
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16. Models in code
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17. Models in Code
• Hey, isn’t there a sample app for that?
• Locations
• https://github.com/HipByte/
RubyMotionSamples/tree/master/ios/
Locations
• MVCS pattern
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18. location.rb (model)
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19. location.rb (entity)
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20. location.rb (properties)
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21. location_store.rb (store)
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22. location_store.rb (MoM)
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23. location_store.rb (psc)
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24. location_store.rb (MoC)
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25. That was easy
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26. Or was it?
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27. Monday, 21 October, 13

28. Overly simplistic
• Doesn’t work with multiple models with
relationships
• You need a reference to an entity, to define
a relationship fully
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29. Chicken & Egg problem
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30. Relationships in code
http://www.slowfamilyonline.com/2011/12/slow-news-day-hooray-for-low-tech-toys/tinkertoys/
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31. Solution
• Define your entities. First.
• Lazily! define your entities’ properties
• properties = (attributes and relationships)
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32. Another example
• Ray Wenderlich’s Failed Bank example has 2
models
• So let’s just start there
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33. Just the entity...
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34. MoM, lazily defined properties
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35. attributes
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36. attributes
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37. relationships
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38. relationships
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39. The “other” model
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40. Relationships
• Done
• With that, you can pretty much define any
kind of model and relationship you want, in
code, no magic required.
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41. Data Loading
https://twitter.com/usmanm/status/388407160159211520/photo/1
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42. iOS Core Data Basics
• Back to Ray
• http://www.raywenderlich.com/12170/coredata-tutorial-how-to-preloadimportexisting-data-updated
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43. The RubyMotion way
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44. Read the data file (JSON)
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45. Add data to store
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46. add_bank
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47. That was easy
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48. Or was it?
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49. How many wells do I
have to load again?
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50. 244,292
Oh.
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51. save for each add
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52. That won’t work
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Read in the whole file first?!?
add, save, add, save
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horribly inefficient for large data loads
add, add, add ...., save once
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yah, never mind
add, add, add, save, add, add, add, save
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better, but still fails on out-of-memory

53. Wait, what?
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54. Back to Core Data
Basics
• Thankfully, Ray figured that out.
• Updated the tutorial to operate as an OS X
(console) app.
• RubyMotion can do that, too.
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55. New, improved load
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56. streaming (CSV) load
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57. create_bank (no save)
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58. saves, every 100
progress every 100/1000
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59. Catch the odd ones
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60. Ta da!
244,292 wells loaded
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61. And then your table
view chokes on 244k
items
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62. Optimization!
http://fineartamerica.com/featured/dont-cross-the-streams-trever-miller.html
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63. Back to Basics (again)
• Ray sure has a lot of good material, doesn’t
he?
• http://www.raywenderlich.com/999/coredata-tutorial-for-ios-how-to-usensfetchedresultscontroller
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64. Why?
• NSFetchedResultsController gives us huge
performance benefits
• Avoids loading all the data in memory at
once
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65. bank_store.rb
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66. failed_bank_table_view_controller.rb
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67. failed_bank_table_view_controller.rb
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68. number of rows
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69. cell for row
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70. configure cell
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71. the delegate
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72. Monday, 21 October, 13

73. DEMO!
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74. That’s All, Folks!
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Questions? Comments?
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@wndxlori
Monday, 21 October, 13
https://github.com/wndxlori/
WNDXRubyMotion/tree/master/FailedBankCD
lori@wndx.com
http://www.linkedin.com/in/loriolson
http://www.wndx.com

75. Core Data in Motion
• It’s an ebook!
• Early pre-release
• http://coredatainmotion.com
Monday, 21 October, 13