Thursday, 8 February 2018

Multi threading? Concurrency? Asynchronous task? GCD (Grand Central Dispatch) ? in Swift Programming

Introduction of Grand Central Dispatch

Grand central dispatch is the powerful api for multitasking with sync and async programming in iOS.

Grand Central Dispatch (GCD) is a low-level API for managing concurrent operations. It will make your application smooth and more responsive. Also helps for improving application performance. Sometimes we are trying to perform multiple tasks at the same time that time most of the developer-facing application hang or freezing issue this is the common issue. That’s why we are using GCD to manage multiple tasks at the same time.

The DispatchQueue API like a company 🏢..Who having staff units like junior level and senior level workers 👷🏼‍. So now the company can take both heavy and light work with 
there team.

DispatchQueue.main.async {
     // Perform your async code here


Concurrenct- It’s starting multiple tasks at the same time but not guarantee for the finish at same time. Its can finish any order.

Serial- It’s executing one task at a time.

Sync vs Async

Sync - When a work item is executed synchronously with the sync method, the program waits until execution finishes before the method call returns.

Code Example Sync

func syncWork(){
        let northZone = DispatchQueue(label: "perform_task_with_team_north")
        let southZone = DispatchQueue(label: "perform_task_with_team_south")
        northZone.sync {
            for numer in 1...3{ print("North \(numer)")}
        southZone.sync {
            for numer in 1...3{ print("South \(numer)") }
    //Call Func here 
//    North 1
//    North 2
//    North 3
//    South 1
//    South 2
//    South 3

Async - execute asynchronously with the async method, the method call returns immediately.

Code Example Async

func asyncWork(){
        let northZone = DispatchQueue(label: "perform_task_with_team_north")
        let southZone = DispatchQueue(label: "perform_task_with_team_south")
        northZone.async {
            for numer in 1...3{ print("North \(numer)") }
        southZone.async {
            for numer in 1...3{ print("South \(numer)") }

//Call Async Task

//    North 1
//    South 1
//    North 2
//    South 2
//    North 3

//    South 3

Perform network task with UI updates -

Global Queue -Using to perform non-UI work in the background.

Main Queue -Using to update the UI after completing work in a task on a concurrent queue.

List of DispatchQueue Priority -



Perform background Quality of Service (QOS) task - .background).async { 
    // Call your background task
    DispatchQueue.main.async { 
       // UI Updates here for task complete.


DispatchQueue with delay ⏳

let deadlineTime = + .seconds(1)
DispatchQueue.main.asyncAfter(deadline: deadlineTime) {
    //Perform code here


Dispatch Groups 👨‍👨‍👦‍👦

let dispatchGroup = DispatchGroup()

loadUseractivities { dispatchGroup.leave() }

loaduserComments { dispatchGroup.leave() }

dispatchGroup.notify(queue: .main) {
    print("all activities complete ")


Wednesday, 7 February 2018

How to calculate height of a multiline String in Swift

Calculate Height of text to set dynamic height for complete Text

import UIKit
extension String {
func heightWithConstrainedWidth(width: CGFloat, font: UIFont) -> CGFloat {      
let constraintRect = CGSize(width: width, height: .greatestFiniteMagnitude)
let boundingBox = self.boundingRect(with: constraintRect,
options: [.usesLineFragmentOrigin, .usesFontLeading],
attributes: [NSFontAttributeName: font], context: nil)
        return boundingBox.height

call this extension in your code
CGFloat TextHeight = (TextLabel.text?.heightWithConstrainedWidth(width:
TextLabel.frame.size.width, font: TextLabel.font))!

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).