Scott M. Nealsmn@automationgarden.com

smn.mg@acmefoo.orgscottmneal@gmail.com

© 2012-2014 AutomationGarden

CoreData:Connecting to the Cloud

an Improvement

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Topics: tonight

Core Data Review iCloud

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Core Data Brief Review

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Why CoreData?

Provides an OO layer for persistent storage• Apple avoids the word “database”• You don’t need to know SQL

• Hardcoded, hacked SQL in apps is a Royal PITA to maintain

Why not just use Defaults?• Defaults doesn’t know about relationships

• The OSX defaults command has limited access to values below the top level• PlistBuddy overcomes this

• It’s up to you to decide to use Defaults or Core Data• but once you know Core Data, it’s hard to leave...

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Entity: Review

Default subclass of NSManagedObjectKinda-sorta like a row in a DB table• but much more OO

Can create custom Entities which utilize Inheritance Hierarchy• Group Cats and Dogs under shared abstract superclass

Mammals• Relationships

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Entity can contain:• Attribute

• type based on value class

• Relationship• types

• one-to-one• one-to-many• many-to-many (via “join table”)

• Returned to caller as an NSSet (unsorted)• Inverse relationships• Delete rules

• No Action/Nullify/Cascade/Deny

• Fetched Property• Returned to caller as an NSArray

Can also store fetch request(s) with an entity

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Core Data Stack: ReviewNSManagedObjectContext is the center of most everything we’ll need to do with Core DataNSPersistentStoreCoordinator talks directly with “database” store• 1 instance per store

• Can handle multiple concurrent instances of NSMangedObjectContext

NSPersistentStore is an object representation of data store

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NSManagedObjectContext

NSPersistentStoreCoordinator

NSPersistentStore

NSManagedObjectModel

NSManagedObjectModel is a compiled version of the .xcdatamodel you create in Xcode

sqlite, xml, ...

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NSManagedObjectContext

The “center of the universe”NOT thread safe by default• http://stackoverflow.com/questions/10593735/

making-core-data-thread-safeNeeded for • Insertion of new NSManagedObject (or subclasses)• Fetching of NSManagedObject (or subclasses)

Handled for you automatically when you use Bindings to wire-up interface to model• Alas, no bindings on iOS (currently...)

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NSPersistentStore*

Each “database” store has one NSPersistentStore instance (and ONLY one) associated with itEach NSPersistentStore has one (and ONLY one) NSPersistentStoreCoordinator • communicates with NSPersistentStore

• Uses NSManagedObjectModel to know how to OO-ify the underlying store into a Core Data NSManagedObjectContext-friendly way

Multiple NSManagedObjectContext instances use a single NSPersistentStoreCoordinator• This ensures data store consistency

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NSManagedObjectModel

A compiled version of the .xcdatamodel you create in XcodeOften abbreviated MOM (Managed Object Model)Contains a complete description of all Entities, including their properties (attributes and relationships), fetch requests, fetch properties, etc.You may assign a version to a MOM via an identifier within the MOM or a key within the MOM’s userInfo • “v1.1”, or “build38release29a” or whatever you want

MOMs can be migrated forward• Difficult to migrate backwards

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Guides to Fetching & Predicates

Apple’s guides:• http://developer.apple.com/library/mac/

#documentation/Cocoa/Conceptual/CoreData/Articles/cdFetching.html

• http://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/Predicates/predicates.html• Predicates not solely for core data

• Spotlight• In-memory filtering

• ...

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Predicate Basics

Most common way to create predicates: predicateWithFormat:• The predicate format string syntax is different from

regular expression syntax• The regular expression syntax is defined by the ICU—see

http://www.icu-project.org/userguide/regexp.html• You can use regex with MATCHES

• The left hand expression equals the right hand expression using a regex-style comparison according to ICU v3

• String comparisons are by default case and diacritic sensitive. You can modify an operator using the key characters c and d within square braces to specify case and diacritic insensitivity respectively, for example firstName BEGINSWITH[cd] $FIRST_NAME.

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Predicate Basics

Have the Predicate Format String Syntax doc handy• http://developer.apple.com/library/mac/

#documentation/Cocoa/Conceptual/Predicates/Articles/pSyntax.html#//apple_ref/doc/uid/TP40001795-CJBDBHCB

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Review: Fetching with Core Data

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NSManagedObjectContext *moc = [self managedObjectContext];NSEntityDescription *entityDescription = [NSEntityDescription    entityForName:@"Employee" inManagedObjectContext:moc];NSFetchRequest *request = [[[NSFetchRequest alloc] init] autorelease];[request setEntity:entityDescription];

// Set example predicate and sort orderings...NSNumber *minimumSalary = ...;NSPredicate *predicate = [NSPredicate predicateWithFormat: @"(lastName LIKE[c] 'Lindsay') AND (salary > %@)", minimumSalary];[request setPredicate:predicate];

NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"firstName" ascending:YES];[request setSortDescriptors:[NSArray arrayWithObject:sortDescriptor]];[sortDescriptor release];

NSError* error = nil;NSArray* array = [moc executeFetchRequest:request error:&error];if (nil == array) || (nil != error){    // Deal with error...}

...

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Review: Insert/Save in Core Data

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NSManagedObjectContext *moc = [self managedObjectContext];NSManagedObject *aUser = [NSEntityDescription insertNewObjectForEntityForName:@"User" inManagedObjectContext:moc];[aUser setValue:@"Scott" forKey:@"name"];[aUser setValue:@"Portland" forKey:@"city"];[aUser setValue:@"Oregon" forKey:@"state"];NSError *error;if (![moc save:&error]) { NSLog(@"Whoops, couldn't save: %@", [error localizedDescription]);}

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Demo Apps:

Road Trip - From “iOS Cloud Development for Dummies”

• Download examples (warts and all) from - http://www.dummies.com/go/iosclouddev

Example iOS7- http://ossh.com.au/design-and-technology/software-development/sample-library-style-ios-core-data-app-with-icloud-integration/

Peruse ADC for anything interesting

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iCloud

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iCloudiCloud: serves iOS and Mac/PC devices• Multi-Application Ecosystem

Can store on iCloud• Key-Value Storage

• Cloud version of NSUserDefaults

• Container• Document Storage

• File• Package• Core Data

• Uses Document Service• to automagically handle changes to/from iCloud servers

iOS 5 or later• Introduced WWDC2011, released October 2011• sorry <=iOS4...

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iCloud

Utilizes Transaction Logs• entire data is not copied each time

Developer doesn’t worry about• making network connection• configuring iCloud itself

Programmer registers for notifications to know when changes have occurred in the cloud• and handles appropriately

Only works on devices, not on simulator

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iCloud EntitlementUses Entitlement called “Ubiquity Container”• Entitlement named NS*Ubiquitous

• not NS*Cloud or UI*Cloud

• Default definition uses your TeamID (or IndividualID) and your BundleID• Seen when logged into Apple Developer Member Center

• example URL:• /var/mobile/Library/Mobile Documents/

J3K73N7L25.senseption.com.neal.RoadTrip/

All need to be coordinated:• Provisioning Profile• AppID• BundleID

• com.apple.developer.ubiquity-kvstore-identifier• com.apple.developer.ubiquity-container-identifiers

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iCloud Entitlement Process1. On Apple Developer Member Center, enable iCloud entitlement/service/capability (for new or old app)

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iCloud Entitlement Process2. Create and Download Provisioning Profile

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iCloud Entitlement Process3. Drag Provisioning Profile into Xcode Organizer (if not done automatically)

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NOT here

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iCloud Entitlement Process4. Enable entitlements/capabilities in the project (if not already done)

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iCloud Key/Value Storage

Not CoreData specific, but a nice featureConflict resolution• Simple: last change wins

Works even when iCloud not enabledStats• Up to 1024 keys• 1MB data per application• Up to 15 requests per 90 seconds

Just like NSDefaults, do NOT store any passwords here• encrypted or otherwise...

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iCloud Key/Value Storage// Get an app’s default storeNSUbiquitousKeyValueStore* kvStore = [NSUbiquitousKeyValueStore defaultStore];

// Register notification to see if data on the cloud has changed[[NSNotificationCenter defaultCenter] addObserver:self selector: @selector(ubiquitousKeyValueStoreDidChange:) name: NSUbiquitousKeyValueStoreDidChangeExternallyNotification object: kvStore];

// Values not stored to/from iCloud until you synchronize[kvStore synchronize];

// Store a value in the kv store[keyStore setString:@”Saved String” forKey:@"MyString"];

// Values not stored to/from iCloud until you synchronize[kvStore synchronize];

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iCloud Key/Value StorageReason that notification was fired is returned in notification

• Initial download from iCloud• Other device modified data (“push”)• Over iCloud quota

// Get an app’s default store- (void)ubiquitousKeyValueStoreDidChange:(NSNotification* theNotif){" NSDictionary* userInfo = [notification userInfo];// get reason for change" int reason = [[userInfo objectForKey:NSUbiquitousKeyValueStoreChangeReasonKey] intValue];// get the changed keys--ONLY the changed keys" NSArray* changedKeys = [userInfo objectForKey:NSUbiquitousKeyValueStoreChangedKeysKey];// store the changed values locally...}

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iCloud Container Storage

Application Container• File Storage area that is app-specific• “Sandbox”

Ubiquity Container• iCloud-specific file storage area

Data (whether document or core) is broken up sort-of-like a tiled image into chunks

• All chunks moved upon first upload to iCloud• Only changed chunks moved when changes made

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iCloud Container Storage

Metadata always pushed via NSMetadataQuery• Clients always know what documents are available to

them from iCloudClient pulls what it wants/needs

• Mac OS X: everything• iOS: app makes request

Data transferred peer-to-peer when possibleAutomatic conflict resolution

• You can also peruse UIDocumentStateInConflictURL Publishing

• Can include as email attachment rather than the document itself

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iCloud Container Storage

Container URL• The network path to desired document• Avoid getting on the main thread

To Check for iCloud availability:• iOS 6 / Mtn Lion (or later):

id token = [[NSFileManager defaultManager] ubiquityIdentityToken];if(token) ...

• iOS 5 / Lion (or later): NSURL *ubiq = [[NSFileManager defaultManager] " URLForUbiquityContainerIdentifier:nil];if (!ubiq) ...

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iCloud Container Storage

Asynchronous method// Register notification to see if iCloud available[[NSNotificationCenter defaultCenter] addObserver:self selector:@(handleUbiquityIdentityChanged:) name:NSUbiquityIdentityDidChangeNotification object:nil];

// Get container URL on not-the-main threaddispatch_async(dispatch_get_global_queue(DISPATCH_PRIORITY_QUEUE_DEFAULT, 0),^{ NSURL *containerURL = [[NSFileManager defaultManager]" URLForUbiquityContainerIdentifier:nil];});

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iCloud Document w/o Core Data

UIDocument / NSDocument1. Determine whether iCloud is enabled on device by

sending• [NSFileManager URLForUbiquityContainerIdentifier:]

• Will return something like • N42E42A42L.com.neal.RoadTrip

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iCloud Document w/o Core Data

2. Add file presenters• Adopt NSFilePresenter protocol• Make all changes through NSFileCoordinator object

• locks file for editing

• prevents background iCloud processes from modifying file at same time your code is

• UIDocument already conforms to NSFilePresenter3. Explicitly move your files to iCloud• Use value returned in step 1 with• [NSFileManager

setUbiquitous:itemAtURL:destinationURL:error]

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iCloud Document w/o Core Data

4. Handle version conflicts for a file• When multiple applications/devices save the same file

to the same container at the same time, iCloud stores both and lets the user decide which is the “right one”

5. Use running NSMetaDataQuery objects to receive notifications from applications/devices as files are added or removed

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iCloud Document w/o Core Data

6. Handle cases where files are in iCloud but are not fully downloaded to local application/device• File is considered fully downloaded when the

application:• Attempts to access the file• Sends the startDownloadingUbiquitousItemAtURL:error

message to NSFileManager

For a user, cloud ignorance is bliss--they just want their document• And you need to track/handle these cases yourself

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iCloud with Core DataDatabase, not DocumentCore Data Storage remains localCore Data Stores that support

• change logs• sqlite

• full file transfer• xml• binary

UIManagedDocument & NSPersistentStore• See http://developer.apple.com/library/ios/

#releasenotes/DataManagement/RN-iCloudCoreData/_index.html

• NSPersistentDocument not supported on iCloudiCloud itself is NOT a Persistent Store--works outside of Core Data

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iCloud with Core DataFeatures

• Per record conflict resolution• Three-way merge• Incremental changes only• Asynchronous Import• Lightweight schema migration

• versioning

Multiple “Local” stores as a best practice• One to hold data that doesn’t belong in the cloud• One to act as a “cache” to iCloud

• Decide if your iCloud store should be available all times

Fallback Store should exist in case user doesn’t enable/use iCloudUse Core Data Migration to pre-populate new store

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iCloud with Core DataUse Data Model Configurations to allow Core Data to split entities across multiple stores

• iCloud vs. LocalSingle Managed Object Context will “do the right thing”

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iCloud with Core Data

//add the store, use the "LocalConfiguration" to make sure state entities all end up in this store and that no iCloud entities end up in it_localStore = [_psc addPersistentStoreWithType:NSSQLiteStoreType configuration:@"LocalConfig" URL:storeURL options:nil error:&localError];

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iCloud with Core Data- (BOOL)loadiCloudStore:(NSError * __autoreleasing *)error{ BOOL success = YES; NSError *localError = nil; NSFileManager *fm = [[NSFileManager alloc] init]; _ubiquityURL = [fm URLForUbiquityContainerIdentifier:nil]; NSURL *iCloudStoreURL = [self iCloudStoreURL]; NSURL *iCloudDataURL = [self.ubiquityURL URLByAppendingPathComponent:@"iCloudData"]; NSDictionary *options = @{NSPersistentStoreUbiquitousContentNameKey : @"iCloudStore", NSPersistentStoreUbiquitousContentURLKey : iCloudDataURL }; _iCloudStore = [self.psc addPersistentStoreWithType:NSSQLiteStoreTypeconfiguration:@"CloudConfig"URL:iCloudStoreURLoptions:optionserror:&localError];

...

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iCloud with Core Data

1. Provide a value for NSPersistentStoreUbiquitousContentNameKey

2. Provide a value for NSPersistentStoreUbiquitousContentURLKey• the value that we saw earlier which was a URL path,

including TeamID and BundleID like • N42E42A42L.com.neal.RoadTrip

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iCloud with Core DataNSFileManager* fileManager = [NSFileManager defaultManager];NSURL* persistentStoreUbiquitousContentURL = [fileManager URLForUbiquityContainerIdentifier:nil];NSString* ubiquityContainerIdentifierPath = [[persistentStoreUbiquitousContentURL path] stringByAppendingPathComponent:@"RoadTripSharedPointOfInterest"];persistentStoreUbiquitousContentURL = [NSURL fileURLWithPath:ubiquityContainerIdentifierPath];options = [NSDictionary dictionaryWithObjectsAndKeys:[NSString stringWithFormat:@"%@%@", @"com.neal.coredata.itineraryR02.", appDelegate.destinationPreference], NSPersistentStoreUbiquitousContentNameKey, persistentStoreUbiquitousContentURL, NSPersistentStoreUbiquitousContentURLKey, [NSNumber numberWithBool:YES], NSMigratePersistentStoresAutomaticallyOption, [NSNumber numberWithBool:YES], NSInferMappingModelAutomaticallyOption, nil];

...

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iOS7 / OSX9 Improvements

Many unhappy campers a year ago...• API forced synchronous sync (slow...)• Apple didn’t realize how many people switched their

iCloud account info on-the-fly• And taking that into consideration was a Royal PITA for us

• Apple admitted there wasn’t a consistent paradigm• realized if the frameworks did it, we’d all be happier

Apple rearchitected iCloud / Core Data integration• Great WWDC2013 preso

• but no downloadable sample code (!)

Good source of downloadable sample codehttp://ossh.com.au/design-and-technology/software-development/sample-library-style-ios-core-data-app-with-icloud-integration/

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iOS7/OSX9 Changes

Fallback Store improvements• Entirely managed by CoreData

• Only one store file per iCloud account• Must be stored in local storage

• preferably App Sandbox• Storing “Local store” in the cloud as a document is now

discouraged

• Auto synched with cloud to ensure a local persistent store exists while you are offline

• Events logged to consoleCore Data: Ubiquity: peerID:StoreName - Using local storage: 1

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iOS7/OSX9 Changes

Asynchronous Setup• New notifications

• these:NSPersistentStoreCoordinatorStoresWillChangeNotification

NSPersistentStoreCoordinatorStoresDidChangeNotification

• encourage you to:-[NSManagedObjectContext save:]

-[NSManagedObjectContext reset:]

• this:NSPersistentStoreDidImportUbiquitousContentChangesNotification

• encourages you to:-[NSManagedObjectContext mergeChangesFromContextDidSaveNotification:]

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iOS7/OSX9 ChangesHandling Account Changes• Old notifications:

• this:NSUbiquityIdentityTokenDidChangeNotification

• would require you to (and handle all cases of):-[NSManagedObjectContext reset:]

-[NSPersistentStoreCoordinator removePersistentStore:]

-[NSPersistentStoreCoordinator addPersistentStore:]

• New (iOS7/OSX9):• this: (look familiar?)

NSPersistentStoreCoordinatorStoresWillChangeNotification

• encourages you to:-[NSManagedObjectContext save:]

-[NSManagedObjectContext reset:]

• which then: (look familiar?)NSPersistentStoreCoordinatorStoresDidChangeNotification

• encourages you to:-[NSManagedObjectContext save:]

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iCloud Accounts and Stores

Provide store URL inside App Sandbox• NOT in cloud

CoreData creates an opaque containerEach iCloud account is tied to a single local storeStore is automatically removed by CoreData when no longer neededSee WWDC2013s207 for more details on API• and sample code here

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iCloud Debugging

Test with multiple devicesXcode5 improvementsiOS simulator improvements

• iCloud Document Storage• iCloud Key-Value Store• Push Notifications

Core Data Logging• NSUserDefaults• com.apple.coredata.ubiquity.logLevel 3

com.apple.CoreData.SQLDebug 1

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iCloud DebuggingiCloud Logging

• OSXubcontrol -k 7

• iOS• iCloud Debug Provisioning Profile

• from developer.apple.com/downloads• Sync with iTunes to get logs

~/Library/Logs/CrashReporter/MobileDevice/device-name/DiagnosticLogs

Monitor Network Traffic• Wireshark

Use airplane mode to induce conflictsConfiguration Profiledeveloper.icloud.com

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iCloud SummaryIt’s Ubiquitous!iCloud Design Guide

• http://developer.apple.com/library/ios/documentation/General/Conceptual/iCloudDesignGuide/iCloudDesignGuide.pdf

WWDC videos• Still watch 2012 videos to get background for iOS5/6

compatibility• WWDC2013s207 also discusses changes to SQLite

interfacingCaveats

• Not cross-platform• Bad taste in people’s mouths from 2012-2013• Learning Curve• CoreData is NOT the same as a database

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Scott M. Nealsmn@automationgarden.com

smn.mg@acmefoo.orgscottmneal@gmail.com

© 2012-2014 AutomationGarden

CoreData:Connecting to the Cloud

an Improvement

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Web Services

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Types of Web ServicesMessage-Oriented • (aka “Big web services”)

• UDDI (Universal Description Discovery and Integration)• WSDL (Web Services Description Language)• SOAP (Simple Object Access Protocol)

• “Chatty”--low signal/noise ratioResource-based• usually REST (REpresentational State Transfer)-HTTP

• Return a Representation of the Resource• XML• JSON• ?

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Request

Response

WebServer

WebService

Request

Response

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Resource-Based Web Services

A URL resource request:• scheme://domain:port/path?querystring#fragment_id• scheme: http, https, etc.

• use https for secure requests

• domain: hostname or IP

• port (optional, scheme-dependent)• path• queryString

• fragment_id (rare in resource requests)Example:• http://maps.googleapis.com/maps/api/geocode/

json?sensor=false&address=17 SE 3rd Avenue, Portland, OR 97214

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Resource-Based Web Services in iOS

Resource representation can come back as XML or JSON• iOS is fluent in both

We’ll start with a synchronously-loaded XML example • RoadTrip 2

We can then look at an asynchronous version• RoadTrip 3

Exercises “for the reader” that we don’t address here• JSON parse (instead of XML)• Creating your own web services

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Road Trip 2

We create a WSManager class and use synchronous URL to get XML and then parse it• See addLocation:...

• which calls geocodeSynchronouslyXML

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Road Trip 3

Asynchronous URL connection requires a delegate and support of the following delegate methods• Specified in Protocol NSURLConnectionDelegate

• primary• connection:didReceiveResponse:• connection:didReceiveData:• connection:didFailWithError:• connectionDidFinishLoading:

• optional• connection:willCacheResponse:• connection:willSendRequest:redirectResponse:• connection:didReceiveAuthenticationChallenge:• connection:didCancelAuthenticationChallenge:

• See addLocation:...• which calls geocodeAsynchronouslyXML

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