Archive for the ‘iOS’ Category

Nextive JSON Parser for iOS and Mac OS – Fast

Thursday, July 21st, 2011

Dear all,

The code with which the Nextive JSON Parser was tested on had a bug, which gave the results we published. After the bug was fixed, the resulting speed wasn’t as fast, although it’s still one of the fastest out there.

The parser, which works for iOS and Mac OS, still has a few things which can improve performance, and we’ll continue working on it until we max it out. In the meantime, we’ll keep posting screenshots with the latest results.

photo1

—–
We released our Nextive JSON Parser for iOS and Mac OS on GitHub:
https://github.com/nextive/NextiveJson

We noticed it performs really well on iOS (images below) when parsing Twitter’s public timeline. Please let us know if it makes a difference in your product!

json-parser-1a json-parser-2a
Credits: Martin Adoue and Hernan Pelassini

Posted in OS, iOS | Comments Off

Core Data

Tuesday, July 5th, 2011

Core Data Introduction

  • Properties List / NSUserDefaults: We can easily persist a lot of common iOS data structures (like NSArray, NSDictionary, NSString, NSNumber, etc) in a plist file. Also we can persist custom objects through NSCoding protocol. The problem with this technique is when we handle big volumes of data, for example if we have 100 records in a plist and we want to read one of those record, we have to load the 100 records in memory first. And if we want to add a record to that list or update some of them, we need to save all records in the plist. As we get more records in a plist we are going to make more unnecessary read/write operations and bad use of memory.
  • SQLite: This is more robust than the first option but is more complex to use. You can use sql syntax to get only the records that you want and update or add records without having to load all records in memory or write all records locally. The API to handle SQLite is a little complex and there isn’t an easy way to persist objects.
  • Core Data: What’s Core Data? Well, basically it’s an ORM (Object-relational mapping) that provides a high level of abstraction. It uses SQLite to persist the objects and it’s available on iOS 3.0 and higher. I think it has the best of the two previous options: it’s easy to use and it’s robust.

Core Data Stack:

We are going to mention the most important classes in Core Data framework:

Core Data Framework

 

  • Managed Object (NSManagedObject): It represents one entity’s instance. If we have an entity called Employee, one managed object represents one employee.
  • Managed Object Context (NSManagedObjectContext): This is the context where the managed objects live.
  • Manged Object Model (NSManagedObjectModel): It represents the data model used to do the mapping between the classes and the relational model.
  • Persistent Store Coordinator (NSPersistentStoreCoordinator): This is a collection of Persistent Object Store classes.
  • Persistent Object Store (NSPersistentObjectStore): It represents a storage (Core Data usually uses SQLite).

Using Core Data

In order to start using Core Data in our project we have to do the following steps:

  1. Add the framework CoreData.framework to the project.
  2. Create a Data Model with Xcode.
  3. Generate the data classes (those classes are subclasses of NSManagedObject.
  4. Create a Managed Object Model with the defined Data Model.
  5. Create the Persistent Store Coordinator with the created Managed Object Model and set a Persistent Object Store on it.
  6. Finally, create a Managed Object Context and set the created Persistent Store Coordinator.

We are going to use the created Managed Object Context to do CRUD operations (create, read, update and delete).

In the next sections we are going to describe deeper the necessary steps to get a Managed Object Context.

Creating a Data Model

The Data Model represents the entities and relationships mainly. It helps to do the mapping of the objects to the persistent store. Those are the necessary steps to create a Data Model using Xcode ver 3.2.x:

Go to the option File >> New File in the menu, select the iOS / Resource group and choose the option Data Model.

Data Model

 

If the project already has data classes we have an option to automatically generate the data model based on that classes. We just have to select which classes we want to add to the data model.

Data Model Classes

 

Finally, we are going to see the tool to create our Data Model. This tool is very straightforward to use. Graphically you can create or update you Data Model.

Data Model Tool

 

You can see that in the Data Model that we have two entities: Team and Match. Team has an attribute called name and it has two relationships with Match. Match represents a game between two teams. It has as attributes: the date of the match, the score of both teams and it has two relationships to the entity Team. We are going to use this data model to describe some CRUD operations.

Every entity can have:

  • Attributes, similar to a field in a record, you can define the type, if it’s optional or not, if it’s indexed, etc.
  • Relationship with other Entities: the relationships can be 1 to 1, 1 to N.
  • Fetched Properties: It’s some kind of mix between relationships and fetches.

Generating Data Classes from the Data Model

Now that we have a data model created, we can automatically create the data classes that represent the entities defined in the model. Every data class is going to represent an instance of one entity. The generated classes are subclasses of NSManagedObject class.

There are two tools to generate these data classes. One tool is integrated with Xcode and the other one it’s a third party tool called Mogenerator (http://rentzsch.github.com/mogenerator/), the main different with the Xcode tool classes is that Mogenerator creates two set of classes per entity: one for machines, one for humans. The machine class can be always be overwritten to match the data model, while the human class with humans’ work is preserved.

I’m going to describe the steps to generate the classes with Xcode ver 3.2.x:

First, We have to be in the Xcode Data Model tool and go to File >> New File in the menu and choose the group Cocoa Touch Class and select Managed Object Class. If we aren’t on the Data Model tool, we are not going to see the final Managed Object Class option.

Managed Object Class

 

Then we have to select the entities from the Data Model that we want to create Data Classes for.

Data Model Entities

 

After this we are going to have the Data Classes generated in our project.

Creating a Managed Object Context

In order to make CRUD (create, read, update, delete) operations we need an instance of a Managed Object Context. To create a Managed Object Context we need to follow these steps:

  1. Create a Managed Object Model with the defined Data Model.
  2. Create a Persistent Store Coordinator with the created Managed Object Model and set a Persistent Object Store on it.
  3. Finally, create a Managed Object Context and set the created Persistent Store Coordinator.

// 1. Create a Managed Object Model with the defined Data Model.

NSManagedObjectModel *managedObjectModel =

[NSManagedObjectModel mergedModelFromBundles:nil];

// 2. Create a Persistent Store Coordinator with the created Managed Object Model and set a Persistent Object Store on it.

NSError *error = nil;

NSPersistentStoreCoordinator *persistentStoreCoordinator =

[[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:managedObjectModel];

if (![persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType

configuration:nil

URL:storeURL options:nil error:&error]) {

NSLog(@”Unresolved error %@, %@”, error, [error userInfo]);

abort();

}

// 3. Create a Managed Object Context and set the created Persistent Store Coordinator.

NSManagedObjectContext *managedObjectContext =

[[NSManagedObjectContext alloc] init];

[managedObjectContext setPersistentStoreCoordinator:persistentStoreCoordinator];

Creating a Managed Object

Now we are going to create two instances for the entity Team and one instance for the entity Match. Match has two relationships with the entity Team. That represents the teams that are going to play on that match.

// Create a new instance of Team (NSManagedObject subclass). We have to set the Entity Name and the created Managed Object Context

Team *localTeam = (Team*)[NSEntityDescription insertNewObjectForEntityForName:@"Team"

inManagedObjectContext:managedObjectContext];

localTeam.name = @”Manchester”;

// Create another instance of Team

Team *visitingTeam = (Team*)[NSEntityDescription insertNewObjectForEntityForName:@"Team"

inManagedObjectContext:managedObjectContext];

visitingTeam.name = @”Barcelona”;

// Create an instance for Match entity with the created Teams

Match *match = (Match*)[NSEntityDescription insertNewObjectForEntityForName:@"Match"

inManagedObjectContext:managedObjectContext];

// We are going to use a random value to set the match’s result

srandom(time(NULL));

match.scoreVisitingTeam = [NSNumber numberWithInt:random()%5];

match.scoreLocalTeam = [NSNumber numberWithInt:random()%5];

match.date = [NSDate date];

match.visitingTeam = visitingTeam;

match.localTeam = localTeam;

// Persist the changes in the Managed Object Context

NSError *error = nil;

if (managedObjectContext != nil) {

if (![managedObjectContext save:&error]) {

NSLog(@”Unresolved error %@, %@”, error, [error userInfo]);

abort();

}

}

Executing Fetches

In order to execute fetches we need to create a NSFetchRequest instance. We need to define an entity name, a predicate and the order of the data result. Then we use the created Managed Object Context to execute the generated NSFetchRequest instance. The Managed Object Context returns an array of NSManagedObject objects.

Fetch Request

// Create a fetch request instance.

NSFetchRequest *fetchRequest = [[[NSFetchRequest alloc] init] autorelease];

// Set the entity.

NSEntityDescription *entity = [NSEntityDescription entityForName:@"Match"

inManagedObjectContext:managedObjectContext];

[fetchRequest setEntity:entity];

// Set the predicate (it returns all matches played by the team “Manchester”)

NSPredicate *predicate = [NSPredicate predicateWithFormat:@"localTeam.name = 'Manchester' or visitingTeam.name = 'Manchester'"];

[fetchRequest setPredicate:predicate];

// Set the order criteria

NSSortDescriptor *sortDescriptor = [[[NSSortDescriptor alloc] initWithKey:@”date”

ascending:YES] autorelease];

[fetchRequest setSortDescriptors:[NSArray arrayWithObject:sortDescriptor]];

// Finally, execute the fetch request

NSError *error = nil;

NSArray *results = [self.managedObjectContext executeFetchRequest:fetchRequest error:&error];

Deleting a Managed Object

In order to delete Managed Objects we need to mark the objects that we want to delete through the Managed Object Context and then persist the changes.

// Get the NSManagedObject instance that we want to delete

Team *team = …;

// Set that NSManagedObject instance as deleted

[managedObjectContext deleteObject:team];

// Persist the changes

NSError *error = nil;

if (![managedObjectContext save:&error]) {

NSLog(@”Unresolved error %@, %@”, error, [error userInfo]);

abort();

}

Updating a Managed Object

In order to update Managed Objects we just have to update its attributes values and then persist the changes.

// Get the NSManagedObject instance that we want to update

Match *match = …;

// Update some attribute

match.date = [NSDate date];

// Persist the changes

NSError *error = nil;

if (![managedObjectContext save:&error]) {

NSLog(@”Unresolved error %@, %@”, error, [error userInfo]);

abort();

}

Next steps

I’m going to mention some topics that you should read if you want to learn more about Core Data:

  • NSFetchedResultController: This is a controller used to optimize the use of memory when we have to show information on a Table View.
  • Versions and Migration: Core Data has some tools to automatically implement updates on our data model.
  • Threading: It’s important to understand how to use Core Data on multithread scenarios.

References

Author: Pablo Romero

Posted in iOS | Comments Off

Nextive sponsoring Adobe en Vivo, Buenos Aires, Argentina on April 2-3

Monday, March 28th, 2011

We are excited to sponsor and present at the Adobe en Vivo conference in Buenos Aires, Argentina on April 2-3.  We will also share cool info on UX and UI design for mobile games.

AdobeenVivoFor more details: http://www.adobenvivo.com/argentina2011/

We look forward to meeting as many folks as possible this weekend! Pls follow @adobeenvivo for updates.

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Posted in Android, Conferences & Events, iOS | Comments Off

iOS 4 Review

Tuesday, June 8th, 2010

On April 8 the iOS 4 was unveiled by Apple.  More than 100 new features are expected, and 1,500 new API’s for developers, but the focus of the announcement covered seven major features.  These features were: Multitasking, Folders for Apps, Mail, iBooks for iPhone, Game Center, Enterprise, and iAd.

Multitasking

iPhones and iPads to date have not been capable of running non-Apple multiple tasks at the same time.  With the launch of iOS 4, the iPhone, iPad, and iPod touch will be able to switch between up to 12 different apps running concurrently.

The way it works is for users to double tap the home button while in an app to bring up a bar at the bottom of the iPhone home screen.  From here they are able to select a different task to switch to.  Users can cycle through their open apps by sliding the bar to the left or right revealing them in groups of four across.

Apple declared that their use of multitasking will better use battery life and run faster as they plan to have an app that gets switched to the background for another app that takes center stage run in a quiet state in the background.  The apps in the background will be ready to reengage where the user left off instantly.

Specific examples where users might benefit from this multitasking capability are Pandora radio and Skype.  So far the Pandora app had to be in the foreground to operate.  Now in iOS 4, the radio will continue even after it is minimized.  Similarly with Skype, it would have to be the foreground app running to receive calls or to show an online status, but this new feature of the iPhone will allow it to operate and receive calls while in the background, and even convert messages to MSM.  Push notifications will continue to work in iOS 4.

Another added multitasking service is task completion.  An app will continue to complete a task even as another app is running.  This will allow an iPhone to continue a download/upload process, for example, even while in the background.  iPhone 3G and iPod touch 2nd generation will not support the multitasking features.

Folders For Apps

Apps will be able to be combined into custom folders in order to save desktop space, and ease organization.  To activate the feature, the user holds their finger on an app until the icon begins to shake.  The user can then drag an icon onto another icon, and a folder will be created.  The iPhone will automatically create a folder name based off of the category the app falls under, i.e. games, news, etc.  A user can also change the name of the folder to something of their choosing.  This effectively increases the maximum number of apps on a single iPhone from 180 to 2,160.

Mail

Improvements were made to Mail built into the iOS 4.  Similar to Mac OSX, users will have the capability to have a unified inbox where multiple email and exchange accounts go to.  Sorting through email will be improved now that users can follow threads for emails.  A user has to tap on an icon which appears numerically corresponding to the number of emails that are in the thread, and another view brings up all of the messages as if it were a sub-inbox.

The other significant improvement to Mail is that users will be able to open attachments in their emails through other apps that can be loaded from the app store.

iBooks on iPhone

iPhone and iPod touch users will be able to access the iPad’s iBook app.  Users only need to buy a book once and the book can be synced with all devices that have the iBook app.  Similar to other ebook reader platforms, users can also sync the page number and bookmarks between the different devices that run the iBook app.

Enterprise

The new iOS 4 will have better data security through encryption of email and attachments.  There will also be API’s available for developers to encrypt their apps, which is key for enterprise publishers.  Another improvement in enterprise is mobile device management for companies who deploy large numbers of iPhones.  There is also the addition of wireless app distribution so companies can distribute apps trough their own servers instead of using iTunes.

Game Center

A social gaming network will be launched in iOS 4 allowing users to challenge friends through push notifications, or enter automatic matchmaking and be paired up with other players of similar skills level.  The gaming center will also include leader-boards (compare against friends or the world) and achievements.

iAD

This is Apple’s new form of mobile advertising: app based ads.  In an app, there will be a bar at the bottom of a screen which, if pressed, will take users to a new page while keeping the app they had open running in the background via multitasking.  The new page will play an ad, much like a television ad, then followed by a menu screen which will give the user viewing the ad different options of what to explore.  This could include more film clips, games, links to other apps, store locators, etc.  Apple expects to share 60% of ad-generated revenue with developers (ads will be sold and managed through Apple).

If you are interested in getting additional technical info please follow this link! http://developer.apple.com/technologies/iphone/whats-new.html

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Posted in iOS, iPhone | Comments Off