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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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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iOS Basics
• Ray Wenderlich!
• http://www.raywenderlich.com/934/core-
data-tutorial-for-ios-getting-started
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It’s not as scary as it looks
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What?
• Models (entities) in code
• Relationships in code
• Loading data
• Optimization
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Models in code
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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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location.rb (model)
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location.rb (entity)
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location.rb (properties)
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location_store.rb (store)
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location_store.rb (MoM)
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location_store.rb (psc)
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location_store.rb (MoC)
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That was easy
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Or was it?
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No content
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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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Chicken & Egg problem
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Relationships in code
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Solution
• Define your entities. First.
• Lazily! define your entities’ properties
• properties = (attributes and relationships)
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Just the entity...
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MoC, lazily defined properties
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attributes
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attributes
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relationships
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relationships
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properties
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The “other” model
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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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Data Loading
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iOS Core Data Basics
• Back to Ray
• http://www.raywenderlich.com/12170/core-
data-tutorial-how-to-preloadimport-
existing-data-updated
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The RubyMotion way
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Read the data file (JSON)
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Add data to store
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add_bank
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That was easy
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Or was it?
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How many wells do I
have to load again?
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244,292
Oh.
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Houston, we have a
problem
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Read in the WHOLE file?
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save for every add?
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That won’t work either
• add, add, add ...., save once
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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New, improved load
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streaming (CSV) load
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create_bank (no save)
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saves, every 100
progress every 100/1000
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Catch the odd ones
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Ta da!
244,292 wells loaded
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And then your table
view chokes on 244k
items
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Optimization
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Back to Basics (again)
• Ray sure has a lot of good material, doesn’t
he?
• http://www.raywenderlich.com/999/core-
data-tutorial-for-ios-how-to-use-
nsfetchedresultscontroller
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Why?
• NSFetchedResultsController gives us huge
performance benefits
• Avoids loading all the data in memory at
once
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bank_store.rb
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failed_bank_table_view_controller.rb
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failed_bank_table_view_controller.rb
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number of rows
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cell for row
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configure cell
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the delegate
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No content
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In Summary
• Create models in code
• Create relationships between models in
code
• Pre-loading data
• LOTS of data
• Efficiently displaying data
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Please use Core Data!
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Core Data in Motion
• It’s an ebook!
• Almost finished!
• http://coredatainmotion.com