Core Data in Motion

Core Data in MotionNSScotland 2013 - Oct 19/20

Monday, 21 October, 13

Who?

• Lori M Olson

• @wndxlori

• on Github too

• and ADN


i Develop• Ruby (mostly)

• Rails

• iOS (RubyMotion)

• JRuby

• Javascript (some)

• jQuery

• Maps/Charts

• Javascript Testing


i Teach

• Ruby on Rails for Real Developers (RoR4Real)

• Rails for iOS Developers (Rails4iOS)

• Ladies Learning Code - Ruby Introduction


i Speak• 2013

• RubyConf AU, NSScotland

• 2012

• Confoo, RailsConf, Aloha RubyConf

• 2011

• jQueryConf, Madison Ruby

• 2010

• Conferencia Rails

• 2009

• RailsConf


Warning:LOTS of code


The Story

• To rewrite a (mobile) web application (WIMBY) as an iOS application

• Using RubyMotion

• WIMBY = Wells In My Back Yard


The Challenges

• LOTS of data

• On a Map

• In a list (table view)

• Filtering by location


Oh, not much dataMonday, 21 October, 13

RubyMotion gems/DSL’s

• Nitron

• MotionDataWrapper

• MotionModel

• MotionMigrate


iOS Basics

• Ray Wenderlich!

• http://www.raywenderlich.com/934/core-data-tutorial-for-ios-getting-started


http://www.raywenderlich.com/934/core-data-tutorial-for-ios-getting-started




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?


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


It’s not as scary as it looksMonday, 21 October, 13

What?

• Models (entities) in code

• Relationships in code

• Loading data

• Optimization


Models in code


Models in Code

• Hey, isn’t there a sample app for that?

• Locations

• https://github.com/HipByte/RubyMotionSamples/tree/master/ios/Locations

• MVCS pattern


https://github.com/HipByte/RubyMotionSamples/tree/master/ios/Locations






location.rb (model)Monday, 21 October, 13

location.rb (entity)Monday, 21 October, 13

location.rb (properties)Monday, 21 October, 13

location_store.rb (store)Monday, 21 October, 13

location_store.rb (MoM)Monday, 21 October, 13

location_store.rb (psc)Monday, 21 October, 13

location_store.rb (MoC)Monday, 21 October, 13

That was easy


Or was it?



Overly simplistic

• Doesn’t work with multiple models with relationships

• You need a reference to an entity, to define a relationship fully


Chicken & Egg problemMonday, 21 October, 13

Relationships in code

http://www.slowfamilyonline.com/2011/12/slow-news-day-hooray-for-low-tech-toys/tinkertoys/




Solution

• Define your entities. First.

• Lazily! define your entities’ properties

• properties = (attributes and relationships)


Another example

• Ray Wenderlich’s Failed Bank example has 2 models

• So let’s just start there


Just the entity...Monday, 21 October, 13

MoM, lazily defined properties


attributesMonday, 21 October, 13

attributesMonday, 21 October, 13

relationshipsMonday, 21 October, 13

relationshipsMonday, 21 October, 13

The “other” modelMonday, 21 October, 13

Relationships

• Done

• With that, you can pretty much define any kind of model and relationship you want, in code, no magic required.


Data Loading

https://twitter.com/usmanm/status/388407160159211520/photo/1




iOS Core Data Basics

• Back to Ray

• http://www.raywenderlich.com/12170/core-data-tutorial-how-to-preloadimport-existing-data-updated


http://www.raywenderlich.com/12170/core-data-tutorial-how-to-preloadimport-existing-data-updated






The RubyMotion wayMonday, 21 October, 13

Read the data file (JSON)Monday, 21 October, 13

Add data to storeMonday, 21 October, 13

add_bankMonday, 21 October, 13

That was easy


Or was it?


How many wells do I have to load again?


244,292Oh.


save for each addMonday, 21 October, 13

That won’t work

• Read in the whole file first?!?

• add, save, add, save

• horribly inefficient for large data loads

• add, add, add ...., save once

• yah, never mind

• add, add, add, save, add, add, add, save

• better, but still fails on out-of-memory


Wait, what?


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.


New, improved loadMonday, 21 October, 13

streaming (CSV) loadMonday, 21 October, 13

create_bank (no save)Monday, 21 October, 13

saves, every 100progress every 100/1000


Catch the odd onesMonday, 21 October, 13

Ta da! 244,292 wells loaded


And then your table view chokes on 244k

items


Optimization!

http://fineartamerica.com/featured/dont-cross-the-streams-trever-miller.html




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


http://www.raywenderlich.com/999/core-data-tutorial-for-ios-how-to-use-nsfetchedresultscontroller






Why?

• NSFetchedResultsController gives us huge performance benefits

• Avoids loading all the data in memory at once


bank_store.rbMonday, 21 October, 13

failed_bank_table_view_controller.rb


failed_bank_table_view_controller.rb


number of rowsMonday, 21 October, 13

cell for rowMonday, 21 October, 13

configure cellMonday, 21 October, 13

the delegateMonday, 21 October, 13


DEMO!


That’s All, Folks!

• Questions? Comments?

• https://github.com/wndxlori/WNDXRubyMotion/tree/master/FailedBankCD

• @wndxlori

• [email protected]

• http://www.linkedin.com/in/loriolson

• http://www.wndx.com


https://github.com/wndxlori/WNDXRubyMotion/tree/master/FailedBankCD




mailto:[email protected]

mailto:[email protected]

http://www.linkedin.com/in/loriolson

http://www.linkedin.com/in/loriolson

Core Data in Motion

• It’s an ebook!

• Early pre-release

• http://coredatainmotion.com


http://coredatainmotion.com

http://coredatainmotion.com

Date post:	18-Oct-2014
Category:	Technology
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Core Data in Motion

Technology