Core Data in MotionRubyMotion #inspect May 28-29, 2014

Lori Olson

• lori@wndx.com

• www.wndx.com

• @wndxlori

• Freelance developer, mentor, trainer

• CANADA!

KUDOSChanging the world, one Thank You at a time!

kudosnow.com

Thanks to my client Kudos, for being understanding about my speaking engagements.

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• 2014

• Scottish Ruby Conference, RubyMotion #inspect

• 2013

• RubyConf AU, NSScotland

• 2012

• Confoo, RailsConf, Aloha RubyConf

• 2011

• jQueryConf, Madison Ruby

• 2010

• Conferencia Rails

• 2009

• RailsConf

The Task

Why?Learning RubyMotion

How?To rewrite a (mobile) web application

as an iOS application

What?Wells In My Back Yard

The Challenges

LOTS of data

On a Map

In a List (table)

Filtering by Location

How hard could it be?

Oh, not that much data

244,292

RubyMotion gems/DSL’s

• Nitron

• MotionDataWrapper

• MotionModel

• MotionMigrate

• many, many others

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

iOS Basics

• Ray Wenderlich!

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

It’s not as scary as it looks

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

location.rb (model)

location.rb (entity)

location.rb (properties)

location_store.rb (store)

location_store.rb (MoM)

location_store.rb (psc)

Persistent Store Coordinator

location_store.rb (MoC)

Managed Object Context

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 problem

Relationships in code

Solution

• Define your entities. First.

• Lazily! define your entities’ properties

• properties = (attributes and relationships)

Just the entity...

Wait a minute...

MoC, lazily defined properties

attributes

attributes

relationships

relationships

properties

The “other” model

More of the same

Relationships

• Done

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

Data Loading

iOS Core Data Basics

• Back to Ray

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

But of course, his way is the Xcode way. We need to translate to RubyMotion.

The RubyMotion way

Inside our store, create a load method

Read the data file (JSON)

Add data to store

Wait, what does add_bank do again?

add_bank

That was easy

Or was it?

How many wells do I have to load again?

244,292 Oh.

Houston, we have a problem

Read in the WHOLE file?

save for every add?

add, save, add, save

That won’t work either

• add, add, add ...., save once

Ok, no, that won’t work either

Batching… ?

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

Looked promising, but still ended up with out of memory errors

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.

Instead of running INSIDE the simulator (in your device)

New, improved load

streaming (CSV) load

create_bank (no save)

saves, every 100 progress every 100/1000

Catch the odd ones

Ta da! 244,292 wells loaded

And then your table view chokes on 244k

items

Optimization

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

Why?

• NSFetchedResultsController gives us huge performance benefits

• Avoids loading all the data in memory at once

bank_store.rb

failed_bank_table_view_controller.rb

failed_bank_table_view_controller.rb

wall of text. let’s break that down

number of rows

cell for row

configure cell

the delegate

In Summary

• Create models in code

• Create relationships between models in code

• Pre-loading data

• LOTS of data

• Efficiently displaying data

Please use Core Data!

Finnegan!

Core Data in Motion

• It’s an ebook!

• Almost finished!

• http://coredatainmotion.com

That’s All, Folks!• Code:

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

• Questions? Comments?

• @wndxlori

• lori@wndx.com

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

• http://www.wndx.com