Saturday, 20 August 2016

iPhone Bluetooth Objective - C Programming

Using Xcode, create a new View-based Application project and name it as Bluetooth.
All the various APIs for accessing the Bluetooth is located in the GameKit framework. Hence, you need to add this framework to your project. Add a new Framework to the project by right-clicking on the Frameworks group in Xcode and selecting Add, Existing Frameworks. Select GameKit.framework

In the BluetoothViewController.h file, declare the following object, outlets, and actions:

@interface BluetoothViewController : UIViewController {
GKSession *currentSession;
IBOutlet UITextField *txtMessage;
IBOutlet UIButton *connect;
IBOutlet UIButton *disconnect;
@property (nonatomic, retain) GKSession *currentSession;
@property (nonatomic, retain) UITextField *txtMessage;
@property (nonatomic, retain) UIButton *connect;
@property (nonatomic, retain) UIButton *disconnect;
-(IBAction) btnSend:(id) sender;
-(IBAction) btnConnect:(id) sender;
-(IBAction) btnDisconnect:(id) sender;

The GKSession object is used to represent a session between two connected Bluetooth devices. You will make use of it to send and receive data between the two devices.
In the BluetoothViewController.m file, add in the following statements in bold:

#import "BluetoothViewController.h"
@implementation BluetoothViewController
@synthesize currentSession;
@synthesize txtMessage;
@synthesize connect;
@synthesize disconnect;

Double-click on BluetoothViewController.xib to edit it in Interface Builder. Add the following views to the View window
  • Text Field
  • Round Rect Button

Perform the following actions:
  • Control-click on the File’s Owner item and drag and drop it over the Text Field view. Select txtMessage.
  • Control-click on the File’s Owner item and drag and drop it over the Connect button. Select connect.
  • Control-click on the File’s Owner item and drag and drop it over the Disconnect button. Select disconnect.
  • Control-click on the Send button and drag and drop it over the File’s Owner item. Select btnSend:.
  • Control-click on the Connect button and drag and drop it over the File’s Owner item. Select btnConnect:.
  • Control-click on the Disconnect button and drag and drop it over the File’s Owner item. Select btnDisconnect:.
Right-click on the File’s Owner item to verify that all the connections are made correctly.

Back in Xcode, in the BluetoothViewController.mfile, add in the following statements in bold:

- (void)viewDidLoad {
[connect setHidden:NO];
[disconnect setHidden:YES];
[super viewDidLoad];
- (void)dealloc {
[txtMessage release];
[currentSession release];
[super dealloc];

Searching for Peer Devices
Now that all the plumbings for the project have been done, you can now focus on the APIs for accessing other Bluetooth devices.
In the BluetoothViewController.h file, declare a GKPeerPickerController object:

#import "BluetoothViewController.h"
@implementation BluetoothViewController
@synthesize currentSession;
@synthesize txtMessage;
@synthesize connect;
@synthesize disconnect;
GKPeerPickerController *picker;

The GKPeerPickerController class provides a standard UI to let your application discover and connect to another Bluetooth device. This is the easiest way to connect to another Bluetooth device.
To discover and connect to another Bluetooth device, implement the btnConnect: method as follows:

-(IBAction) btnConnect:(id) sender {
picker = [[GKPeerPickerController alloc] init];
picker.delegate = self;
picker.connectionTypesMask = GKPeerPickerConnectionTypeNearby;
[connect setHidden:YES];
[disconnect setHidden:NO];
[picker show];

When remote Bluetooth devices are detected and the user has selected and connected to one of them, the peerPickerController:didConnectPeer:toSession: method will be called. Hence, implement this method as follows:
- (void)peerPickerController:(GKPeerPickerController *)picker
didConnectPeer:(NSString *)peerID
toSession:(GKSession *) session {
self.currentSession = session;
session.delegate = self;
[session setDataReceiveHandler:self withContext:nil];
picker.delegate = nil;
[picker dismiss];
[picker autorelease];
When the user has connected to the peer Bluetooth device, you save the GKSession object to the currentSession property. This will allow you to use the GKSession object to communicate with the remote device.
If the user cancels the Bluetooth Picker, the peerPickerControllerDidCancel: method will be called. Define this method as follows:
- (void)peerPickerControllerDidCancel:(GKPeerPickerController *)picker
picker.delegate = nil;
[picker autorelease];
[connect setHidden:NO];
[disconnect setHidden:YES];

To disconnect from a connected device, use the disconnectFromAllPeers method from the GKSession object. Define the btnDisconnect: method as follows:
-(IBAction) btnDisconnect:(id) sender {
[self.currentSession disconnectFromAllPeers];
[self.currentSession release];
currentSession = nil;
[connect setHidden:NO];
[disconnect setHidden:YES];
When a device is connected or disconnected, the session:peer:didChangeState: method will be called. Implement the method as follows:
- (void)session:(GKSession *)session
peer:(NSString *)peerID
didChangeState:(GKPeerConnectionState)state {
switch (state)
case GKPeerStateConnected:
case GKPeerStateDisconnected:
[self.currentSession release];
currentSession = nil;
[connect setHidden:NO];
[disconnect setHidden:YES];
Handling this event will allow you to know when a connection is established, or ended. For example, when the connection is established, you might want to immediately start sending data over to the other device.

Sending Data

To send data to the connected Bluetooth device, use thesendDataToAllPeers: method of the GKSession object. The data that you send is transmitted via an NSData object; hence you are free to define your own application protocol to send any types of data (e.g. binary data such as images). Define themySendDataToPeers: method as follows:
- (void) mySendDataToPeers:(NSData *) data
if (currentSession)
[self.currentSession sendDataToAllPeers:data
Define the btnSend: method as follows so that the text entered by the user will be sent to the remote device:
-(IBAction) btnSend:(id) sender
//---convert an NSString object to NSData---
NSData* data;
NSString *str = [NSString stringWithString:txtMessage.text];
data = [str dataUsingEncoding: NSASCIIStringEncoding];
[self mySendDataToPeers:data];

Receiving Data

When data is received from the other device, thereceiveData:fromPeer:inSession:context:method will be called. Implement this method as follows:
- (void) receiveData:(NSData *)data
fromPeer:(NSString *)peer
inSession:(GKSession *)session
context:(void *)context {
//---convert the NSData to NSString---
NSString* str;
str = [[NSString alloc] initWithData:data encoding:NSASCIIStringEncoding];
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Data received"
[alert show];
[alert release];
Here, the received data is in the NSData format. To display it using the UIAlertView class, you need to convert it to an NSString object.

Testing the Application

That’s it!
You are now ready to test the application. Press Command-R in Xcode to deploy the application onto two iPhones / iPod Touches. For this article, I assume you have two devices -- either iPhones or iPod Touches. In order to run this application,  they both need to run at least iPhone OS 3.0.
Once the application is deployed to the two devices, launch the application on both devices. On each device, tap the Connect button. The GKPeerPickerController will display the standard UI to discover other devices .
After a while, both application should be able to find each other  When you tap on the name of the found device, the application will attempt to connect to it. 

Steps to follow to submitting iPhone/iPad Apps To The Apple App Store

Step 1:

Certificate is an essential element to submit or test an application on iPhone. It comes with code sign(Signatures) which would verified when an application is submitted on apple store or when tested on iPhone.
One can bypass these if an application is installed on jail-break iPhone or  when submitted on Cydia but this is not possible when one wants submit it to AppStore.

One has to through 2 step procedure to create a certificate from developer portal. I copied those two from “iPhone developer portal”
  •  Generating Certificate Signing Request
  •  Submitting a Certificate Signing Request for Approval
Generating a Certificate Signing Request:
  •  Open the Utilities folder and launch Key chain Access from the Applications folder.
  •  Set the value of Online Certificate Status Protocol (OCSP) and Certificate Revocation List (CRL) to “off” in the Preferences Menu.
  •  Select Key chain Access -> Certificate Assistant -> Request a Certificate from a Certificate Authority.
  •  Fill in your email address in User Email Address Field. Confirm that this email address is same as provided at the time of registering as iPhone developer.
  •  Fill in your name in the Common Name field. Confirm that this name is same as provided at the time of registering as iPhone developer.
  • It is not necessary to have an Certificate Authority (CA). The ‘Required’ message would be eliminated after finishing the following step.
  • Click the ‘save to disk’ radio button if prompted, choose ‘Let me specify key pair information’ and proceed.
  •  If  you choose ‘Let me specify key pair’ option then one has provide a file name and click ‘Save’. Select ‘2048 bits’ for Key Size and ‘RSA’ for the algorithm in next screen and proceed.
  •  CSR file would created on the desktop by Certificate Authority.
Submitting a Certificate Signing Request for Approval:
  •  Once CSR file is created log in to the iPhone developer program portal and go to ‘Certificates’> ‘Development’ and select ‘Add Certificate’.
  •  Click the ‘Choose file’ button, select your CSR and click ‘Submit’. The portal will reject the CSR if Key Size is not set to 2048 bit at the time of CSR creation.
  • This will followed by notification to Team Admins by email of the certificate request.
  •  The change in the certificate status would informed by email on approval or rejection of the CSR by Team Admin.
Download/Installing Certificate on your machine
  •  Once the CSR is approved the Team Members and Team Admins can download their certificates via the ‘Certification’ section of the Program Portal.  Choose ‘Download’ next to the certificate name to download your iPhone development certificate to your local machine.
  •  Once this is done double-click the .cer file to launch Key chain Access and install your certificate.
            On installation of certificate on your MAC the next step is to create an App ID.

 Step 2:

Follow the following steps to create an App ID:
  • Go to ‘App IDs’ and click ‘App ID’ after logging in to iPhone developer program portal.
  •  Populate the ‘App Id Name’ field with your application name (that is – iPhone app) and in ‘App Id’ enter something like com.yourdomain.applicationname (i.ecom.companyname.iPhoneapp) and click submit.
  •  Please do note down the “App Id” as this would be utilized in Info.plist, bundle identifier tag.
 Step 3:

Next step would be to create a Provisioning file for our X code and is the last step for creating binary which would submit it to App Store.
  • After you navigate to ‘Provisioning’> ‘Distribution’ click ‘Add Profile’ in iPhone developer program portal.
  •  Choose “App Store” in “Distribution Method”.
  •  In “Profile Name” enter your application name (i.e iPhone app) which will be your provisioning profile name as well.
  • In “App ID” select the app name(i.e. iPhone app) which you created in Step 2.
  • After downloading the Provisioning profile copy it to your/YourUserName/Library/MobileDevice/Provisioning Profile.
Step 4:

Now everything is step up, open your project in Xcode
  •  Click “i” Info button after selecting your project from “Group & File” in left side bar.
  •  Navigate to “Configuration” tab and select “Release”. Click the “Duplicate” button from bottom, name is “iPhone Distribution”.
  •  Click on “Build” tab and choose “iPhone Distribution” and enter in “Search in Build Settings” filed ‘Base SDK’ and select the current selected Device and  change to what gadget your application is targeting.
  • Now in “Search in build setting” field enter “code signing identity” and choose the provisioning profile created earlier in Step 3. Apply the same to the child property “Any iPhone OS Device”.
  • Once this done close the Info screen and select the “Target”> “Your App” from “Group & File” in left side bar and click on “Info” button again from X code.
  •  To be on the safer side repeat step 3 and 4.
  •  With the Info screen still open click on “Properties” tab and enter “App Id”(i.e. com.companyname.iPhoneapp) in Identifier field.
  •  Now that all is done, click on “Build” (cmd+B) from X code>Build.
  •  You will find your binary file created on right clicking on “Product”> “YourApp” and selecting “Reveal in Finder”. Zip this file.
Step 5:

The next step is to submit the binary file created to iTunes connect.
  • In your browser type  and login using your iPhone developer account.
  • Click on “Manage Your Account” > “Add Application”
  • On replying to a simple question from apple you can submit your application to app store. You also need few things in your system before you submit your application.
a) Application Name (must be unique)
b) Application description
c) Application Category
d) URL for your application feedback.
e) Icon of your application in 512 x 512 size.
f) Main picture of your application in 320 x 480 or 320 x 460 size.
(You have option to submit up to 4  more pictures of your application).

Wednesday, 17 September 2014

you should know what is the use of @property.

  •  @property offers a way to define the information that a class is intended to encapsulate. If you declare an object/variable using @property, then that object/variable will be accessible to other classes importing its class. 

    If you declare an object using @property in the header file, then you have to synthesize it using @synthesize in the implementation file. 

    .h class

    @interface ExampleClass : NSObject
    @property (nonatomic, retain) NSString *name;

    .m class
    @implementation ExampleClass
    @synthesize name;

    Now the compiler will synthesize accessor methods for name.
  • ExampleClass *newObject=[[ExampleClass alloc]init];
    NSString *name1=[newObject name]; // get 'name'
    [obj setName:@“Tiger”];

    • List of attributes of @property :
      • atomic.
      • nonatomic.
      • retain.
      • copy.
      • readonly.
      • readwrite.
      • assign.
      • strong.
    atomic : It is the default behaviour. If an object is declared as atomic then it becomes thread-safe. Thread-safe means, at a time only one thread of a particular instance of that class can have the control over that object.
    Example : 
    @property NSString *name; //by default atomic
    @property (atomic)NSString *name; // explicitly declared atomic
    nonatomic: It is not thread-safe. You can use the nonatomic property attribute to specify that synthesized accessors simply set or return a value directly, with no guarantees about what happens if that same value is accessed simultaneously from different threads. For this reason, it’s faster to access a nonatomic property than an atomic one. 
    @property (nonatomic)NSString *name;  
    • retain: is required when the attribute is a pointer to an object.The setter method will increase retain count of the object, so that it will occupy memory in autorelease pool.
    @property (retain)NSString *name;
    • copy: If you use copy, you can't use retain. Using copy instance of the class will contain its own copy.
    Even if a mutable string is set and subsequently changed, the instance captures whatever value it has at the time it is set. No setter and getter methods will be synthesized.
    @property (copy) NSString *name;
    NSMutableString *nameString = [NSMutableString stringWithString:@"Liza"]; = nameString;    
    [nameString appendString:@"Pizza"];

     readonly: If you don't want to allow the property to be changed via setter method, you can declare the property readonly.
    @property (readonly) NSString *name;
    • readwrite: is the default behaviour. You don't need to specify readwrite attribute explicitly.

    @property (readwrite) NSString *name;
    • assign: will generate a setter which assigns the value to the instance variable directly, rather than copying or retaining it. This is best for primitive types like NSInteger and CGFloat, or objects you don't directly own, such as delegates.

    @property (assign) NSInteger year;

    Strong:-is a replacement for retain.

    @property (nonatomic, strong) AVPlayer *player;
The strong keyword implies ownership of the property. This is the default, so you don't have to explicitly use the keyword if you intend for the property to have a strong reference. If you declare a property as strong, that property will stay in memory as long as at least one object has a strong reference to it.

The weak keyword implies no ownership or responsibility. If you declare a property as weak, it will be released if the object has no strong references to it. Assigning an object to a weak property does not increase the retain count of that object as it would if the property were declared as strong.

  • unsafe_unretained: There are a few classes in Cocoa and Cocoa Touch that don’t yet support weak references, which means you can’t declare a weak property or weak local variable to keep track of them. These classes include NSTextView, NSFont and NSColorSpace,etc. If you need to use a weak reference to one of these classes, you must use an unsafe reference.
An unsafe reference is similar to a weak reference in that it doesn’t keep its related object alive, but it won’t be set to nil if the destination object is deallocated.
@property (unsafe_unretained) NSObject *unsafeProperty;

Tuesday, 2 September 2014

Filtering a NSArray using NSPredicate

In this post, i'll walk you through how to filter an NSArray using NSPredicates. 
The first thing you'll need to decide is if you're filtering a number or a string.
For strings, you can use any of the following filters: (NOTE: must be all caps)
  • LIKE
For numbers, you can use:
  • !=
  • >
  • >=
  • <
  • <=
  • ==
Now that you know what kind of data you're going to filter on, we can build our predicate.
Lets first assume we're filtering an array of strings:

NSArray* data = @[@"Grapes", @"Apples", @"Oranges];
Using this array, lets filter on the letter "a"
This means we'll want to use CONTAINS.
So if we want to build a hard-coded string it would look something like:
NSString* filter = @"%K CONTAINS %@";
We'll then take our filter string and create a predicate with it: 
NSPredicate* predicate = [NSPredicate predicateWithFormat:filter, @"SELF", @"a"];
Now we can get our filtered out data:
NSArray* filteredData = [data filteredArrayUsingPredicate:predicate];
The result will be an array that contains 2 values:
"Grapes" and "Oranges"
Hmm.... why wasn't "Apples" included, it clearly contains the letter "a". 
Well, b/c the "a" is a capital "A" it wasn't included. 
In order for it to be included, we need to tell the filter to be case insensitive. We do that by passing the parameter "c"
NSString* filter = @"%K CONTAINS[c] %@";
Now, if we rerun our filter with this new string, there will be 3 values returned.
Its worth noting that there is one additional parameter you can also pass in: "d". It stands for diacritic insensitive. So if you wanted your filter to be both case and diacritic insensitive just use:
NSString* filter = @"%K CONTAINS[cd] %@";
i'm sure, you may be wondering what the %K is in the filter string is. That represents the property for each item in the array that we're filtering on. Because our array is just an array of strings, we're not filtering on a particular property. So in this case, we're passing in "SELF".  
Lets pretend we have a more complex object now. We'll call it Person and it has a property called "firstName".
If we wanted to filter on our array of Person objects, we would have to just modify the values we pass in to our predicate:
NSPredicate* predicate = [NSPredicate predicateWithFormat:filter, @"firstName", @"a"];
When we pass this predicate into filteredArrayUsingPredicate: our Person array will be filtered with Person objects whose firstName contains the letter "a".
To take this one step further, lets add a lastName property to our Person object. 
How do we filter both the firstName and lastName properties at the same time?
For this scenario, the requirement is that we want to filter our Person array by any first or last name that contains the letter a. 
To do this, we'll need to use a different method to create our NSPredicate: predicateWithFormat:argumentArray:
We'll also need a new filter string:
NSString* filter = @"%K CONTAINS[cd] %@ || %K CONTAINS[cd] %@";
Then we need to build an array of arguments. The array is just made up of all of the arguments that make up the missing fields in the filter string: 
NSArray* args = @[@"firstName", @"a", @"lastName", @"a"];
Finally we can build our predicate:
NSPredicate* predicate = [NSPredicate predicateWithFormat:filter argumentArray:args];
We can then take that predicate and filter our array the way we did above.

Saturday, 30 August 2014

what is appDelegate?

The AppDelegate is sort of like the entry point for your application.  It implements UIApplicationDelegate and contains methods that are called when your application launches, when is going to the background (i.e. when you hit the home key), when it’s opened back up, and more.  The AppDelegate object is stored as a property on the UIApplication class and is accessible from anywhere in your objective-C classes.  The header and implementation file for your AppDelegate is generated when you create your project and you don’t have to make any modifications for it to work.  However, that doesn’t mean we can’t make changes and make use of the AppDelegate.  We’re going to keep this simple and just add a newNSString property to the delegate.

AppDelegate is handling special UIApplication states.This lets you do initialization/cleanup of your app at the right time.So basically the delegate is responsible for monitoring when it is safe to open/close things, terminate the app etc, and it talks to the application, and gives it accurate & critical information, with regards to how & when to do these tasks?.

The only way I can imagine it, is a security guard who is called by the staff inside a building, and asked if it is safe to open the security door; he can answer YES or NO

1. applicationDidFinishLaunching: – for handling on-startup configuration and construction. which will be called when the app has finished launching

2. applicationWillTerminate: – for cleaning up at the end You should avoid putting other functionality in the AppDelegate since they don’t really belong there.Many people lump these things into their AppDelegate because they are lazy or they think the AppDelegate controls the whole program. You should avoid centralizing in your AppDelegate since it muddies the areas of concern in the app and doesn’t scale.

a delegate is an object that another object defers to on behavior and informs about changes in its state.
The AppDelegate just sits there doing nothing, waiting to be told that something potentially important will happen. The application/iPhone OS is the one doing the work and calling the AppDelegate and it might want to respond to in your code.