Category Archives: iOS

Serializing Data – domain model to persistence

August 30, 2016iOSadmin

http://nshipster.com/nscoding/

There are many ways you serialize data, or convert domain model to persistence:

Core Data
NSKeyedArchiver
pList
NSUserDefault
etc…

Core Data may not be your answer because:

Not all apps need to query data.
Not all apps need automatic migrations.
Not all apps work with large or complex object graphs.

NSKeyArchiver and NSCoding

Thus, using NSKeyArchiver and NSCoding maybe a great solution in some cases.

NSCoding is a simple protocol, with two methods: -initWithCoder: and encodeWithCoder:. Classes that conform to NSCoding can be serialized and deserialized into data that can be either be archived to disk or distributed across a network.

NSKeyArchiver serializes -compliant classes to and from a data representation.

NSCoding delegates

This is so that you can tell it what properties to encode into objects. Encode means to “convert into a coded form”.
Hence, we inject our properties into encodeObject.

Decode means to convert a coded message into something readable.
Thus, that’s why we have our properties take on data returned by the decoder.

Each property is encoded or decoded as an object or type, using the name of the property of as the key each time.

@interface Book : NSObject <NSCoding>

@property NSString *title;

@property NSString *author;

@property NSUInteger pageCount;

@property NSSet *categories;

@property (getter = isAvailable) BOOL available;

@end

@implementation Book

#pragma mark - NSCoding

- (id)initWithCoder:(NSCoder *)decoder {

self = [super init];

if (!self) {

return nil;

}

self.title = [decoder decodeObjectForKey:@"title"];

self.author = [decoder decodeObjectForKey:@"author"];

self.pageCount = [decoder decodeIntegerForKey:@"pageCount"];

self.categories = [decoder decodeObjectForKey:@"categories"];

self.available = [decoder decodeBoolForKey:@"available"];

return self;

}

- (void)encodeWithCoder:(NSCoder *)encoder {

[encoder encodeObject:self.title forKey:@"title"];

[encoder encodeObject:self.author forKey:@"author"];

[encoder encodeInteger:self.pageCount forKey:@"pageCount"];

[encoder encodeObject:self.categories forKey:@"categories"];

[encoder encodeBool:[self isAvailable] forKey:@"available"];

}

@end

File System

NSKeyedArchiver and NSKeyedUnarchiver provide a convenient API to read / write objects directly to / from disk.

1	[NSKeyedArchiver archiveRootObject:books toFile:@"/path/to/archive"];

1	[NSKeyedUnarchiver unarchiveObjectWithFile:@"/path/to/archive"];

You first get the path of the directory you want. Then you append a file name to that path. The resulting NSString appFile is your full path to the file you are saving to.

Then, use your Array or Dictionary, and insert it into NSKeyedArchiver’s archiveRootObject toFile method in order to save.
When you want to load, use unarchiveObjectWithFile:appFile.

NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);

NSString *documentsDirectory = [paths objectAtIndex:0];

NSString *appFile = [documentsDirectory stringByAppendingPathComponent:@"set.txt"];

NSMutableArray *myObject=[NSMutableArray array];

[myObject addObject:self.settings];

[NSKeyedArchiver archiveRootObject:myObject toFile:appFile];

NSMutableArray* myArray = [NSKeyedUnarchiver unarchiveObjectWithFile:appFile];

pLists

A property list (a.k.a. pList) is a structured data representation used by Cocoa and Core Foundation as a convenient way to store, organize, and access standard types of data. You can build little more complex structures but not that much. NSString, NSData, NSNumber, NSDate, NSArray, NSDictionary – these are the only Objective-C data types that property list supports. Sub-entries are only allowed with NSDictionary or NSArray. A property list is used to store “less than a few hundred kilobytes” of data. A very significant and popular use of property lists is to define application settings.

If you open a pList with Xcode this is how it will show a very comfortable view of key-value pairs. But if you open the pList with a text editor you will see the actual format, which is XML. Property list is a subset of XML.

ARC vs MRC

August 29, 2016iOSadmin

https://www.quora.com/How-does-garbage-collection-happen-in-iOS
http://stackoverflow.com/questions/6385285/why-doesnt-ios-have-automatic-garbage-collection

Manual Reference Counting has the developer take care of the allocation and release of the object life cycle by using new/delete, alloc/release. You have to make sure every alloc is matched with a release.

MRC behind the wheel :
1. Every time you create and allocate an object, you increase the reference count of the variable. So suppose you created object foo , so now the reference count got increased to 1.
2. If any other object is also referring to this object, then the count increases to 2.
3. Now if I decide to remove my ownership and i want to remove my reference, then the reference count drops by -1;

So technically, every reference to an object is referenceCount++ and every release of the object is a referenceCount–

Once the reference count reaches zero, that’s when the object foo becomes eligible garbage collection.

Automatic Reference Counting – the iOS compiler looks after the memory management. Thus, you don’t have to worry about releasing the objects. You just allocate and that’s it.

In other words, it is a memory management enhancement where the task of keeping track of reference counting for objects is removed from the programmer and onto the compiler.

ARC differs from Cocoa’s garbage collection [4] in that there is no background process doing the deallocation of objects.[5] Unlike garbage collection, ARC does not handle reference cycles automatically. It is up to the program to break cycles using weak references.[6]

Developers no longer have to worry about retain / release of objects, you don’t have a garbage collector process slowing execution randomly, and you still maintain fairly tight control over memory usage.

How ARC works

ARC works its magic at compile time to do the reference counting for you thereby making it unnecessary (and actually non-allowed) to use any other sort of memory management.

Now what ARC does is it looks up your code, sees where the scope of the variable ends and then adds autorelease, on those objects, and release is deprecated.
So what autorelease does is it adds the object to AUTORELEASE POOL , which basically means once the scope/block ends, objects in that block will be sent release messages.

Why it does not use Garbage Collection

At WWDC 2011, Apple explained that they didn’t want garbage collection on their mobile devices because they want apps to be able to run with the best use of the provided resources, and with great determinism. The problem with garbage collection is not only that objects build up over time until the garbage collector kicks in, but that you don’t have any control over when the garbage collector will kick in. This causes non-deterministic behavior that could lead to slowdowns that could occur when you don’t want them.

Bottom Line: You can’t say, “OK. I know that these objects will be freed at X point in time, and it won’t collide with other events that are occurring.”

How to load profile info

August 10, 2016iOS, Projectsadmin

Declare the header file for EpamAuth:

1	#import "EpamAuth.h"

Then declare a property that conforms to the Authorization interface.

@interface ViewController ()

{

}

@property (nonatomic, strong) id <Authorization> auth;

@end

Then initialize the property in init or a lazyloading accessor

1	self.auth = [EpamAuth defaultAutho];

Finally, use it like this:

[self.auth loginAndGetProfileDataForController:self

withCompletion:^(NSError *error, NSDictionary * profile) {

if(!error && profile) {

NSLog(@"%@", [profile objectForKey:@"city"]);

NSLog(@"%@", [profile objectForKey:@"country"]);

NSLog(@"%@", [profile objectForKey:@"department"]);

NSLog(@"%@", [profile objectForKey:@"jobTitle"]);

NSLog(@"%@", [profile objectForKey:@"givenName"]);

NSLog(@"%@", [profile objectForKey:@"mail"]);

NSLog(@"%@", [profile objectForKey:@"telephoneNumber"]);

NSLog(@"%@", [profile objectForKey:@"usageLocation"]);

NSLog(@"%@", [profile objectForKey:@"userPrincipalName"]);

}

}];

If its your first time logging in, you will have a login window appear. Sign in using your EPAM credentials.

If you have previously logged in, your authentication token will be saved in the keychain, and you don’t have to log in a second time. You simply will be automatically logged in.

To log out:

//log out the current user

[self.auth logoutWithCompletion:^(NSError *error) {

NSLog(@"logged out");

}];

Protected: Download async images into your table

August 9, 2016iOS, Projectsadmin

Protected: Block Storage on Azure using iOS

August 3, 2016iOSAzureadmin

Adding and Removing Observer in UIView

July 26, 2016iOSadmin

ref – http://stackoverflow.com/questions/8200775/when-to-unsubscribe-from-a-nsnotification-in-a-uiview

In your UIView custom class:

- (void)didMoveToWindow {

if (self.window) {

NSLog(@"Added to a window, similar to -viewDidLoad.");

// Subscribe to notifications here.

[[NSNotificationCenter defaultCenter] addObserver:self

selector:@selector(topicAndEntry:)

name:INSERT_TOPIC_ENTRY

object:nil];

[[NSNotificationCenter defaultCenter] addObserver:self

selector:@selector(topicAndEntry:)

name:INSERT_REQUIRED_KEY_VALUE

object:nil];

}

- (void)willMoveToWindow:(UIWindow *)newWindow {

if (newWindow == nil) {

NSLog(@"Will be removed from window, similar to -viewDidUnload.");

// Unsubscribe from any notifications here.

[[NSNotificationCenter defaultCenter] removeObserver:self

name:INSERT_TOPIC_ENTRY

object:nil];

[[NSNotificationCenter defaultCenter] removeObserver:self

name:INSERT_REQUIRED_KEY_VALUE

object:nil];

}

Protected: from data structure to JSON and back in iOS

July 23, 2016C/C++/Objective-C, iOSJSONadmin

Protected: How to get User Data with minimal access to “management AAD portal”

June 17, 2016C/C++/Objective-C, iOS, Node JS, ProjectsAzureadmin

Converting existing Project to read from Azure Backend

May 5, 2016C/C++/Objective-C, iOSAzureadmin

Import Data Model

File >> New >> File >> Data Model. Name it “Activities”.

Ctrl + click >> Show in Finder. Then drag that file onto a text editor such as sublime. You will see basic xml file.

Drag and drop an existing data model file onto the text editor. Copy and paste all the content into your Activities file. Save and close. Your data model should be now updated. Your iOS data model is ready.

Basic Core Stack Class

Create a basic core data stack class with a context, MOC, and PSC.
Make sure the your sql file name, and the data model name are specified.

core data demo

#define DATA_MODEL_FILENAME @”Activities”
#define SQL_FILENAME @”Activities.sqlite”

QSTodoService

Azure should generate a QSTodoService object that does all the reading and writing of data for you.

Unfortunately, it also generates core data code that sits in your AppDelegate. Pull all the core data code out onto your own CoreDataStack class so that AppDelegate is clean.

Then, make these modifications to your QSTodoService:

Use your core stack and its context in QSTodoService’s init method. Commented out code is the original.

#import "CoreDataStack.h"

...

-(QSTodoService *)init

{

self = [super init];

if (self)

{

.....

//QSAppDelegate *delegate = (QSAppDelegate *)[[UIApplication sharedApplication] delegate];

CoreDataStack * coreDataStack = [CoreDataStack defaultStack];

//NSManagedObjectContext *context = delegate.managedObjectContext;

NSManagedObjectContext *context = coreDataStack.privateQueueContext;

...

}

return self;

}

ViewController

conform to NSFetchedResultsControllerDelegate protocol

@interface ActivityViewController () <NSFetchedResultsControllerDelegate>

// Private properties

@property (strong, nonatomic) QSTodoService * todoService;

@property (strong, nonatomic) NSFetchedResultsController * fetchedResultsController;

@property (weak, nonatomic) IBOutlet UITableView *activitiesTableView;

@property (nonatomic, strong)NSMutableArray *activitiesArr;

@end

specify what/how you want to fetch for the fetchedResultsController

- (NSFetchedResultsController *)fetchedResultsController {

if (_fetchedResultsController != nil) {

NSLog(@"%s - valid fetchedResultController, just get it", __FUNCTION__);

return _fetchedResultsController;

}

NSLog(@"%s - nil fetchedResultController, we create one", __FUNCTION__);

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

//QSAppDelegate *delegate = (QSAppDelegate *)[[UIApplication sharedApplication] delegate];

CoreDataStack * coreDataStack = [CoreDataStack defaultStack];

//NSManagedObjectContext *context = delegate.managedObjectContext;

NSManagedObjectContext * context = coreDataStack.privateQueueContext;

fetchRequest.entity = [NSEntityDescription entityForName:@"TodoItem" inManagedObjectContext:context];

// show only non-completed items

fetchRequest.predicate = [NSPredicate predicateWithFormat:@"complete == NO"];

// sort by item text

fetchRequest.sortDescriptors = @[[NSSortDescriptor sortDescriptorWithKey:@"createdAt" ascending:YES]];

// Note: if storing a lot of data, you should specify a cache for the last parameter

// for more information, see Apple's documentation: http://go.microsoft.com/fwlink/?LinkId=524591&clcid=0x409

NSFetchedResultsController *theFetchedResultsController =

[[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest

managedObjectContext:context sectionNameKeyPath:nil

cacheName:nil];

if(!theFetchedResultsController) {

NSLog(@"%s - uh oh, fetchedResultsController NOT successfully created", __FUNCTION__);

}

self.fetchedResultsController = theFetchedResultsController;

_fetchedResultsController.delegate = self;

return _fetchedResultsController;

}

In the viewDidLoad, make sure you create your QSTodoService because we are going to implement a refresh method that uses it to sync all the data between your app the backend service.

- (void) refresh {

//[self.refreshControl beginRefreshing];

NSLog(@"%s - syncData START", __FUNCTION__);

[self.todoService syncData:^ {

//[self.refreshControl endRefreshing];

NSLog(@"%s - syncData complete", __FUNCTION__);

}];

}

- (void)viewDidLoad {

[super viewDidLoad];

// Create the todoService - this creates the Mobile Service client inside the wrapped service

self.todoService = [QSTodoService defaultService];

NSError *error;

if (![[self fetchedResultsController] performFetch:&error]) {

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

exit(-1); // Fail

}

// load the data

[self refresh];

...

}

use the fetchedResultsController to get the objects

#define TABLE_ATTRIBUTE_TITLE @"event_title"

#define TABLE_ATTRIBUTE_AUTHOR @"author"

#define TABLE_ATTRIBUTE_DATE @"event_date"

#define TABLE_ATTRIBUTE_NUM_OF_PARTICIPANTS @"num_of_participants"

....

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath

{

NSManagedObject *item = [self.fetchedResultsController objectAtIndexPath:indexPath];

cell.accessoryType = UITableViewCellAccessoryDisclosureIndicator;

...

NSDate * date = (NSDate*)[item valueForKey: TABLE_ATTRIBUTE_DATE];

NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];

[dateFormatter setDateFormat:@"MMMM dd"];

NSString * dateString = [dateFormatter stringFromDate: date];

cell.activityTimeLbl.text = dateString;

cell.activityNameLbl.text = [item valueForKey: TABLE_ATTRIBUTE_TITLE];

cell.activitySponsorLbl.text = [item valueForKey: TABLE_ATTRIBUTE_AUTHOR];

NSNumber * numOfParticipants = [item valueForKey:TABLE_ATTRIBUTE_NUM_OF_PARTICIPANTS];

cell.participantsLbl.text = [numOfParticipants stringValue];

cell.publishTimeLbl.text = activity.publishTime;

cell.activitySponsorImg.image = [UIImage imageNamed:activity.sponsorImgStr];

return cell;

}

Programmatically add a Navigation Controller to your project

April 22, 2016iOSadmin

objective C demo
swift 3 demo

AppDelegate.swift

SWIFT 3

import UIKit

@UIApplicationMain

class AppDelegate: UIResponder, UIApplicationDelegate {

var window: UIWindow?

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {

// Override point for customization after application launch.

self.window = UIWindow(frame: UIScreen.main.bounds)

// create navigation

let nav1 = UINavigationController()

// instantiate your basic view controller

let mainView = ViewController(nibName: nil, bundle: nil) //ViewController = Name of your controller

// set our navigation's view array

nav1.viewControllers = [mainView]

// app root view controller is on navigation

self.window!.rootViewController = nav1

self.window?.makeKeyAndVisible()

self.window?.backgroundColor = UIColor.cyan

return true

}

func applicationWillResignActive(_ application: UIApplication) {

// Sent when the application is about to move from active to inactive state. This can occur for certain types of temporary interruptions (such as an incoming phone call or SMS message) or when the user quits the application and it begins the transition to the background state.

// Use this method to pause ongoing tasks, disable timers, and invalidate graphics rendering callbacks. Games should use this method to pause the game.

}

func applicationDidEnterBackground(_ application: UIApplication) {

// Use this method to release shared resources, save user data, invalidate timers, and store enough application state information to restore your application to its current state in case it is terminated later.

// If your application supports background execution, this method is called instead of applicationWillTerminate: when the user quits.

}

func applicationWillEnterForeground(_ application: UIApplication) {

// Called as part of the transition from the background to the active state; here you can undo many of the changes made on entering the background.

}

func applicationDidBecomeActive(_ application: UIApplication) {

// Restart any tasks that were paused (or not yet started) while the application was inactive. If the application was previously in the background, optionally refresh the user interface.

}

func applicationWillTerminate(_ application: UIApplication) {

// Called when the application is about to terminate. Save data if appropriate. See also applicationDidEnterBackground:.

}

ViewController

import UIKit

import CoreLocation

class ViewController: UIViewController {

override func viewDidLoad() {

super.viewDidLoad()

self.view.backgroundColor = UIColor.red

let openAction = #selector(openNewWindow(sender:))

let openWindowBtn = UIButton(type: UIButtonType.custom)

openWindowBtn.addTarget(self, action: openAction, for: UIControlEvents.touchUpInside)

openWindowBtn.frame = CGRect(x: 80, y: 80, width: 200, height: 80)

openWindowBtn.setTitle("Push Window", for: .normal)

openWindowBtn.backgroundColor = UIColor.orange

self.view.addSubview(openWindowBtn)

}

func openNewWindow(sender: Any) {

print("CLICKED")

self.navigationController?.pushViewController(CustomViewController(), animated: true)

}

override func didReceiveMemoryWarning() {

super.didReceiveMemoryWarning()

// Dispose of any resources that can be recreated.

}

deinit {

print("\(type(of: self), #function) - deinit")

}

CustomViewController.swift

import UIKit

class CustomViewController: UIViewController {

override func viewDidLoad() {

super.viewDidLoad()

self.view.backgroundColor = UIColor.brown

// Do any additional setup after loading the view.

}

override func didReceiveMemoryWarning() {

super.didReceiveMemoryWarning()

// Dispose of any resources that can be recreated.

}

deinit {

print("\(type(of: self), #function)")

}

OBJECTIVE C

The whole idea is that your window strongs UINavigationController, and UINavigationController strongs your main ViewController.

The UINavigationController is set up in your AppDelegate. Then your UINavigationController is init-ed with your main view controller.

Then, in your main view controller, use self.navigationItem to set up the buttons and title.

UINavigationController

First we create a UINavigationController property.

@interface AppDelegate ()

@property(nonatomic, retain) UINavigationController * navigationController;

@end

Then, we create the UINavigationController and init it with the main view controller of your project.
Set the UINavigationController as the root view controller of our window.

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {

ViewController * mainViewController = [[ViewController alloc] init];

self.navigationController =

[[UINavigationController alloc] initWithRootViewController: mainViewController];

self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];

[self.window setRootViewController:self.navigationController];

self.window.backgroundColor = [UIColor blackColor];

[self.window makeKeyAndVisible];

return YES;

}

In your main view controller, make sure in your viewDidLoad, you set the navigation button like so:

- (void)viewDidLoad {

[super viewDidLoad];

// UI set up

UIBarButtonItem * navButton =

[[UIBarButtonItem alloc] initWithTitle:@"add" style:UIBarButtonItemStylePlain target:self action:@selector(addPerson:)];

self.navigationItem.rightBarButtonItem = navButton;

}

The nav button has a button responder:

-(void)addPerson:(id)sender {

}

This means when you click on the nav button, we want to navigate to a new view controller. Hence, let’s implement the view controller that we want to navigate to.

File >> New >> File >> Cocoa Touch Class

Put in AddViewController for the “class name”.
Put in UIViewController for the “subclass of”.

Then import AddViewController to your main view controller, and implement the button responder like so:

-(void)addPerson:(id)sender {

AddViewController * vc = [[AddViewController alloc] init];

[self.navigationController pushViewController:vc animated:YES];

}

Make sure you set background color for every view controller because if its default as clear, there may be animation issues.