IPhone: Pass data between view controllers

There are several ways to pass the data between the view controllers.

1.      Delegates & Protocols

2.      NSUserDefaults

3.      Database

4.      Singleton Object

Here I am going to explain using Delegates & Protocols.
First we will get an idea about the protocols and delegates.

Protocols

 Protocols declare methods that can be implemented by any class. Protocols are useful in at least three situations:

·         To declare methods that others are expected to implement

·         To declare the interface to an object while concealing its class

·         To capture similarities among classes that are not hierarchically related

 Declaring a Protocol

You declare formal protocols with the @protocol directive:

@protocol ProtocolName

method declarations

@end

Optional Protocol Methods

Protocol methods can be marked as optional using the @optional keyword. Corresponding to the @optional modal keyword, there is a @required keyword to formally denote the semantics of the default behavior. You can use @optional and @required to partition your protocol into sections as you see fit. If you do not specify any keyword, the default is @required.

@protocol MyProtocol

- (void)requiredMethod;

@optional

- (void)anOptionalMethod;

- (void)anotherOptionalMethod;

@required

- (void)anotherRequiredMethod;

@end

Delegates

iOS uses Objective-C delegates to implement the delegation pattern, in which one object passes work off to another. The object doing the work is the delegate of the first object. An object tells its delegate to do work by sending it messages after certain things happen.
Delegates are basically a way of extending the behavior of a class without needing to create subclasses. Applications in iOS often use delegates when one class calls back to another after an important action occurs.

For Java Developers:

Protocol is similar to Interface

Protocol	Interface
@protocol ProtocolName -(void)methodName(NSString *):value; @end	public interface ProtocolName {    public void methodName(String value); }
Declare protocol in .h file and import the .h file, wherever protocol has to be called	implements the interface and have a logic in a class

Sample Code : Here 

Screenshots:

View Controller Loaded

Entered Sample Text and Pressed Updated Button

Data transferred to Second View controller

 

Edited the Text and Pressed Back

Edited Text updated in first view controller

 

IPhone: Solution for [[UIDevice currentDevice] uniqueIdentifier]]

[[UIDevice currentDevice] uniqueIdentifier] is deprecated in iOS5

APPLE DOCUMENTATION:
To create a unique identifier specific to your app, you can call the CFUUIDCreate function to create a UUID, and write it to the defaults database using the NSUserDefaults
/*
 * Generates UUID using CFUUIDCreate
 */
- (NSString *) generateUUID
{
    NSString *  result;
    CFUUIDRef   uuid;
    CFStringRef uuidStr;
    
    uuid = CFUUIDCreate(NULL);
    assert(uuid != NULL);
    
    uuidStr = CFUUIDCreateString(NULL, uuid);
    assert(uuidStr != NULL);
    
    result = [NSString stringWithFormat:@"%@", uuidStr];
    assert(result != nil);
    
    CFRelease(uuidStr);
    CFRelease(uuid);
    
    return result;
}

// Use the Below Code to save the UUID into the NSUserDefaults, so that we can use, anywhere in the application.
NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
NSString *fetchUUID = [defaults objectForKey:@"UUID"];
if (fetchedUUID == nil || [fetchedUUID isEqualToString:@""])
{
     NSLog(@"Checking in if");
     [defaults setObject:[self generateUUID] forKey:@"UUID"];
}    
fetchUUID = [defaults objectForKey:@"UUID"];

Use the above code to get UUID in iOS5.

Learn Objective-C for Java Developers

For more information refer book:
Learn Objective-C for Java Developers by James Bucanek from Apress.

Java : Apple Push Notification Server Side Coding

JavaPNS is a Java library to send notifications through the Apple Push Notification Service to iOS devices. Using JavaPNS, we can send Push notification in a single line of code.

For further details, refer site : http://code.google.com/p/javapns/

The Apple Push Notification Service is a service created by Apple Inc. 

iOS apps can provide three types of notifications:

• Sounds: Plays an audible alert
• Alerts/Banners: Displays an alert or banner on the screen
• Badges: Displays an image or number on the application icon

 Before sending a notification from server, we need to have the following.

1. Device Token of the device (IPhone/IPod).
2. Private Key created from certificate.
3. Have a password of the private key created.

Note: If the private key is not proper, SSLHandshakeException occurs

For Eg:

Java Code looks like

Push.alert(message, keystore, password, production, devices)

Push.alert("Hello World!", "keystore.p12", "keystore_password", false, "Your token");

Parameters:

message : Content to pass

keystore : Private key

password : Private key password

producation : If true, production else sandbox

devices : one or more device token, device token length is 64 digits. The device token is analogous to a phone number; it contains information that enables APNs to locate the device on which the client application is installed.

To run the server code, required jar files list

bcprov-1.45.jar

commons-io-1.3.jar

commons-logging-1.1.1.jar

JavaPNS_2.2.jar

log4j-1.2.16.jar


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Developer view : iOS View controller LifeCycle from Android Activity LifeCycle

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