Native API Deep Dive: Data Storage and Retrieval JAM819

Alan Wong (@alanhhwong)

Ranbijay Kumar (@Ranbijay)

November 29-30, 2012

Files and File System

Not as boring as it sounds!

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Data, Data, and more Data

No big surprise:

Apps need data

It’s like food for your app!

Cascades and native applications have

many options for storing and retrieving data

Surprise:

We’ve got Perimeters to Consider (Spoiler Alert)

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Files vs. Databases

Apps have the ability to:

Read and write to/from the file system

Create files and folders

Create databases

Make database queries

Retrieve data from a server on a network

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Enterprise Allow a Corporate client to secure and manage their resources on the device.

User Users maintain

freedom to use

device to meet

their personal

needs.

BlackBerry Experience

Seamlessly access applications and data from all perimeters (e.g. unified inbox and calendar)

Securing corporate data while

enabling a user’s personal

experience on a single device

BlackBerry Balance

technology delighting both

end users and CIOs

BlackBerry Balance Blending Work and Personal

BlackBerry Balance

Work applications:

•Can access work data and can view only personal data

•Can attach personal files to work email or calendar entries

•Can access intranet using BlackBerry Bridge, corporate VPN or Wi-Fi

Personal applications:

•Cannot access work data

•Cannot attach work files to personal email messages or calendar entries

Work

Applications

Work or Personal

Applications

Personal

Applications

BES email, contacts calendar,

memo & tasks Photo viewer

Social apps

(YouTube, Facebook, etc.)

BlackBerry Bridge & Viewer Media player App World downloads

BlackBerry Browser Document viewer

(Adobe, Docs to go, etc.) Web browser

Work Applications File application Video Chat

Defining Work vs. Personal Applications

Work Perimeter

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File System

Your application runs in a “sandbox”

There are directories in the sandbox for:

Data

Assets

your compiled app

etc

Not all directories are yours to use

That would just be silly.

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File System

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Files – C access

Files are still cool!

FILE *fp;

fp = fopen( "report.dat", "r" );

if( fp != NULL )

{

/* rest of code goes here */

fclose( fp );

}

10

Files – Qt Access

Cascades provides a sexy C++ interface

Uses iostreams, couldn’t be easier

QFile textfile("data/files/text/newfile.txt");

textfile.open(QIODevice::WriteOnly | QIODevice::Text);

QTextStream out(&textfile);

out << "This is a text file\n";

textfile.close();

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File System Paths

Cascades has a class that provides access to the sandbox:

QDir

Also provided are static functions that give access to the different paths

QDir::currentPath() – path to the apps working directory

QDir::homePath() – returns the app’s data directory path

QDir::tempPath() – access to the app’s temp directory

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File System Permissions

Not all the directories viewable are accessible

app

Compiled application, assets, source

data

This is where you store your data. The $HOME environment variable is this directory

db

The application's database files.

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File System Permissions

logs

System logs for an application. The application's stderr and stdout are redirected to this directory.

shared

Subfolders that contain shared data grouped by type. All applications can read from this directory. An application can write to this directory only if the access_shared permission is specified.

tmp

The application's temporary working files.

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JSON

Not Jason

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What is JSON?

A streamlined data structure

Effective way to distribute data either from a server or in a local file

JSON is based on two fundamental ideas:

A collection of name/value pairs (an object)

An ordered list of values (an array)

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What does JSON look like?

[

{

"firstName" : "Mike",

"lastName" : "Chepesky",

"employeeNumber" : 01840192

},

{

"firstName" : "Westlee",

"lastName" : "Barichak",

"employeeNumber" : 47901927

}

]

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Cascades’ Data Access and Model

It’s MVC Baby!

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DataAccess and DataModel

Cascades provides a data model that allows easy cosumption and presentation.

External data ( JSON file or database) is loaded by a DataAccess object

The loaded data is then organized by a DataModel class

Cascades provides ListView classess to present DataModel objects

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DataModels

A data model provides the information to display in a list.

DataModel can be extended for a custom representation of your data

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ListViews

A list view determines how the data in your list is displayed in your app

Must be associated with a DataModel

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DataAccess and JSON

#include <bb/data/JsonDataAccess>

// create a data model with sorting keys for firstname and lastname

GroupDataModel *model = new GroupDataModel(QStringList() << "firstname" << "lastname");

// load the json data

JsonDataAccess jda;

QVariant list = jda.load("contacts.json");

// add the data to the model

model->insertList(list.value<QVariantList>());

// create a ListView control and add the model to the list

ListView *listView = new ListView();

listView->setDataModel(model);

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Databases

We’ve got databases!

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SQLite, QtSql, Cascades API

Native applications can use a variety of ways to interface with databases

Important to remember – it’s all SQLite underneath!

SQLite is not the only open source project that we made available!

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C and libsqlite

Packaged with the tools is SQLite

It comes as libsqlite

It’s available, but we highly recommend that if you are using C++ use QtSql

If you are creating a Cascades application, we have an interface for that too!

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QtSQL Code… oh so easy!

#include <QSqlDatabase>

...

QSqlDatabase db = QSqlDatabase::addDatabase("QPSQL");

db.setHostName("myserver");

db.setDatabaseName("mydb");

db.setUserName("myusername");

db.setPassword("mypassword");

bool ok = db.open();

if(ok)

{

QSqlQuery query("SELECT * FROM *");

}

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Once Again

This is Cascades simple MVC model.

It applies to JSON, and database access.

So simplie.

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Cascades

#include <bb/data/SqlDataAccess>

// create a data model with sorting keys for firstname and lastname

GroupDataModel *model = new GroupDataModel(QStringList() << "firstname" << "lastname");

// load the sql data from contacts table

SqlDataAccess sda("contacts.db");

QVariant list = sda.execute("select * from contact order by firstname");

// add the data to the model

model->insertList(list.value<QVariantList>());

// create a ListView control and add the model to the list

ListView *listView = new ListView();

listView->setDataModel(model);

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Cascades

#include <bb/cascades/ListView>

ListView follows MVC Of course it does!

accepts input from the user (such as item selections or

scrolling)

instructs the model and view

to perform actions based on that input.

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Take Away

Files are easy to access

The file system protects your application, the user, and is useable

Just like a mobile computing platform should be.

Data can be stored, content shared, and private info is safe.

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Stuff to Remember

SQLite is on the platform

A few different ways to access the database

libsqlite – if you like, and you are doing straight C coding

(but why would you)

QtSQL – C++ data access, wrapped in QtCore object

QSqlConnection

Cascades MVC – Integrate your application with awesome components and simple to use ListViews

DataAccess, DataModel, ListView

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… And a few Quick Notes

Don’t forget to fill out the Conference Survey at the Registration Desk to claim a free gift!

THANK YOU for helping us make this

event such a great success!!!

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THANK YOU

JAM819

Alan Wong (@alanhhwong)

Ranbijay Kumar (@Ranbijay)

November 29-30, 2012