Button Types

A button’s type defines its basic appearance and behavior. After creating a button, you cannot change its type. The most commonly used button types are the Custom and System types, but use the other types when appropriate

• UIButtonTypeCustom

  No button style.
  

• UIButtonTypeSystem

  A system style button, such as those shown in navigation bars and toolbars.
  

• UIButtonTypeDetailDisclosure

  A detail disclosure button.
  

• UIButtonTypeInfoLight

  An information button that has a light background.
  

• UIButtonTypeInfoDark

  An information button that has a dark background.
  

• UIButtonTypeContactAdd

  A contact add button.
  

When creating a custom button—that is a button with the type custom—the frame of the button is set to (0, 0, 0, 0) initially. Before adding the button to your interface, you should update the frame to a more appropriate value.

UITableView is a subclass of UIScrollView. Classes that follow the UITableViewDelegate protocol also follow the UIScrollViewDelegate protocol. UITableView can be useful for showing long or indeterminate lists through its cells, whilst UIScrollView is better for when the size of the views to be shown is known beforehand.

The UIView class defines a rectangular area on the screen and the interfaces for managing the content in that area. At runtime, a view object handles the rendering of any content in its area and also handles any interactions with that content.

CAAnimation is an abstract animation class. It provides the basic support for the CAMediaTiming and CAAction protocols. To animate Core Animation layers or Scene Kit objects, create instances of the concrete subclasses CABasicAnimation, CAKeyframeAnimation, CAAnimationGroup, or CATransition.

Whenever you do something on a separate thread, which happens when using queues, it's important to maintain thread safety. Some methods, in particular ones for UIViews, may not work and/or crash on threads other than main thread. Also, make sure not to change anything (variables, properties, etc.) that is also being used on the main thread, unless you are accounting for this change

• Use startPoint and endPoint to change the orientation of the CAGradientLayer.
• Use the locations to affect the spread/positions of the colors.

UIWebView Delegate functions:-

Objective-C Declerations

- (BOOL)webView:(UIWebView *)webView 
shouldStartLoadWithRequest:(NSURLRequest *)request 
 navigationType:(UIWebViewNavigationType)navigationType;

- (void)webView:(UIWebView *)webView 
didFailLoadWithError:(NSError *)error;

- (void)webViewDidFinishLoad:(UIWebView *)webView;

- (void)webViewDidStartLoad:(UIWebView *)webView;

There are different types of date format that you can set: Here is full list of them.

There are many more, for getting different time based on zone(z), for getting time with millisecond details(S), etc.

Referencing self.navigationItem assumes that the UIViewController is embedded inside a UINavigationController.

Beacons are IOT objects. We are focusing on those which conform to iBeacon protocol a Apple standard. Each beacon is a one way device which transmits 3 things

1. UUID
2. Major
3. Minor

We can scan iBeacons by setting up our CLLocation manager object to scan for beacons for particular UUID. All beacons with the given UUID will be scanned.

CLLocation manager also gives call on enter and exit of beacon region.

The NSURLSession class and related classes provide an API for downloading content. This API provides a rich set of delegate methods for supporting authentication and gives your app the ability to perform background downloads when your app is not running or, in iOS, while your app is suspended.

At a high level, NSURLSession is based around the concept of sessions and tasks. A task represents a single request for a single URL (or a single upload to a single URL). A session is a group of related requests.

The operating system provides a single preexisting session—the shared session, which basically works like NSURLConnection. Additionally, you can create your own sessions in your app as needed.

Different apps use sessions in different ways. Many apps create a single session on launch and just keep reusing it. Other apps benefit from being able to cancel a group of related tasks (e.g. a web browser canceling all outstanding requests when you close a tab), and thus create one session to hold each group of related requests.

The first step when using NSURLSession is to create a session configuration object. The (usually) reusable object contains various session settings that you can tweak for your particular needs, such as maximum concurrency, extra headers to send with each request, whether to allow requests to be sent over the cellular radio (iOS only), timeouts, credential storage, minimum TLS version, and even proxy settings.

There are three types of session configurations, depending on how you want the resulting session to behave:

• Default configurations create sessions that work much like NSURLConnection.
• Background configurations create sessions in which requests happen out-of-process, allowing downloads to continue even when the app is no longer running.
• Ephemeral configurations create sessions that do not cache anything to disk, do not store cookies to disk, etc. and thus are suitable for backing things like incognito browser windows.

When you create a background configuration, you must provide a session identifier that allows you to reassociate the background session later (if your app exits or is suspended or terminated by the OS). You must not have more than one instance of a session with the same identifier active in your app, so as a rule, these configurations are not reusable. All other session configurations can be reused to create as many sessions as you want. So if you need to create multiple sessions with similar settings, you can create the configuration once and reuse it every time you create a new session.

After you create a session, you can create tasks in that session. There are three types of tasks:

• Data tasks return data as an NSData object. These are suitable for general use, but are not supported in background sessions.
• Download tasks return data as a file on disk. These are suitable for larger requests, or for use in background sessions.
• Upload tasks upload data from an NSData object or from a file on disk. You provide a data object or file that provides the POST body. The body data/file that you provide on the task overrides any body data/file provided in the NSURLRequest object (if applicable).

Each of these types lets you obtain the response data in a couple of different ways—either by using block-based callbacks or by providing a delegate on the session and implementing delegate methods.

Additionally NSURLSession lets you provide delegate methods for handling authentication, performing custom TLS certificate handling (both for client certificates and server validation), changing the caching behavior, and so on.

1. When you support universal links, iOS 9 users can tap a link to your website and get seamlessly redirected to your installed app without going through Safari. If your app isn’t installed, tapping a link to your website opens your website in Safari.
2. Generally, any supported link clicked in Safari, or in instances of UIWebView/WKWebView should open the app.
3. For iOS 9.2 and less, this will only work on a device. iOS 9.3 also supports the simulator.
4. iOS remembers the user’s choice when opening Universal Links. If they tap the top-right breadcrumb to open the link in Safari, all further clicks will take them to Safari, and not the app. They can switch back to opening the app by default by choosing Open in the app banner on the website.

The CGContextRef opaque type represents a Quartz 2D drawing destination. A graphics context contains drawing parameters and all device-specific information needed to render the paint on a page to the destination, whether the destination is a window in an application, a bitmap image, a PDF document, or a printer.

KVC :- Key-Value Coding

Normally instance variables are accessed through properties or accessors but KVC gives another way to access variables in form of strings. In this way your class acts like a dictionary and your property name for example “age” becomes key and value that property holds becomes value for that key.

For example, you have employee class with "age" property. Normally we access like this.
emp.age = @”20″;
NSString age = emp.age; 

But KVC works like this: 
[emp valueForKey:@"age"]; 
[emp setValue:@"25" forKey:@"age"];

KVO :- Key-Value Observer

The mechanism through which objects are notified when there is change in any of property is called KVO. Ex.:keyboard notification

For example, person object is interested in getting notification when accountBalance property is changed in BankAccount object. To achieve this, Person Object must register as an observer of the BankAccount’s accountBalance property by sending an addObserver: forKeyPath: options: context: message.

The CAShapeLayer class draws a cubic Bezier spline in its coordinate space. The shape is composited between the layer's contents and its first sublayer.

Categories can be used to override methods of a class. Even if the method is actually private. The overridden method cannot be accessed from the category or anywhere else. So it's important to make sure when adding methods to an existing class, that those methods don't exist already.

In iOS9 and above your app must list any URL schemes it will want to query. This is done by adding LSApplicationQueriesSchemes to Info.plist

iOS has built-in support for the tel, http/https ,sms, mailto, facetime schemes. It also supports http–based URLs for Youtube, Maps and iTunes apps.

Examples of built-in URL schemes:

tel: tel://123456890 or tel:123456890

http: http://www.google.com

facetime: facetime://[email protected]

mailto: mailto://[email protected]

sms: sms://123456890 or sms:123456890

Youtube: https://www.youtube.com/watch?v=-eCaif2QKfA

Maps:

• Using address: http://maps.apple.com/?address=1,Infinite+Loop,Cupertino,California

• Using coordinates: http://maps.apple.com/?ll=46.683155557,6.683155557

iTunes: https://itunes.apple.com/us/artist/randy-newman/id200900

Note: Not all special characters are supported in tel scheme (for example * or #). This is done because of security concerns to prevent users from unauthorized redirect of calls, so in this case Phone app won't be opened.

Adding a new RLMObject to an existing Realm - Schema and Migrations

Adding new model classes to a Realm does not require a migration or a schema version bump; only making changes to an existing Realm.

// Content size category constants
UIContentSizeCategoryExtraSmall
UIContentSizeCategorySmall
UIContentSizeCategoryMedium
UIContentSizeCategoryLarge
UIContentSizeCategoryExtraLarge
UIContentSizeCategoryExtraExtraLarge
UIContentSizeCategoryExtraExtraExtraLarge

// Accessibility sizes
UIContentSizeCategoryAccessibilityMedium
UIContentSizeCategoryAccessibilityLarge
UIContentSizeCategoryAccessibilityExtraLarge
UIContentSizeCategoryAccessibilityExtraExtraLarge
UIContentSizeCategoryAccessibilityExtraExtraExtraLarge

As you build adaptive apps, keep in mind the limitations of size classes: they are generalizations, not specific guides for exact pixel sizes or devices. Never attempt to determine what device your app is running on, or whether it's in a split-screen mode, based on the size classes.

Instead, make high-level layout decisions on size class, and use Auto Layout to change precise view frames. (See also the UIViewController method viewWillTransition(to:with:) for a more precise notification of how big a controller's view will be after a transition.)

IBOutlet is neither a reserved word nor a variable or class, is syntactic sugar for Interface Builder. After the Objective-C source code is pre-processed it is resolved to nothing.

In Swift it's resolved as nil.

It's declared in <UIKit/UINibDeclarations.h> as

#ifndef IBOutlet
#define IBOutlet
#endif

UISplitViewController is a container class like UITabViewController, UINavigationController. It separates the main view into two View Controllers masterViewController(PrimaryViewController) and detailViewController(SecondaryViewController). we can send an array with two view controllers and Apple recommends to to UISplitViewController as a rootviewcontroller for your application. To interact between the viewcontrolers I use NSNotificationCenter.

In iOS 8 and later, you can use the UISplitViewController class on all iOS devices, in previous versions of iOS, the class is available only on iPad. UISplitViewController is a container class like UITabViewController, UINavigationController. It separates the main view into two UIViewControllers masterViewController(PrimaryViewController) and detailViewController(SecondaryViewController). we can send an NSArray with two UIViewControllers and Apple recommends UISplitViewController as a rootviewcontroller for your application. To interact between the UIViewControllers I use NSNotificationCenter.

The UIDevice class provides a Singleton instance representing the current device. From this instance you can obtain information about the device such as assigned name, device model, and operating-system name and version.

Run xcodebuild from the directory containing your project to build an Xcode project. To build an Xcode workspace, you must pass both the -workspace and -scheme options to define the build. The parameters of the scheme will control which targets are built and how they are built, although you may pass other options to xcodebuild to override some parameters of the scheme.

import AVKit, import AVFoundation.

UIDatePicker does not inherit from UIPickerView, but it manages a custom picker-view object as a subview.

Content Compression Resistance Priority

This value determines how resistant a view is to being compressed, or shrunk. A higher value here means the view will be less likely to be compressed and more likely to stay the same.

Content Hugging Priority

This value determines how resistant a view is to being expanded. You can imagine “hugging” here to mean “size to fit” – the bounds of the view will “hug” or be close to the intrinsic content size. A higher value here means the view will be less likely to grow and more likely to stay the same.

MPVolumeView only shows up when building and running on an actual iOS device and will not work in a simulator.

• Forget static layouts, constraint issues and warning explosions in the console.
• Forget all the glue code, all the boilerplate code and all the very common overly engineered unnecessary pile of garbage code in your apps.
• Build and make changes to your UI quickly in a snap.
• Make your UI reusable.
• Focus on creating your app, not fighting layout issues.
• Minimal setup, minimal impact on your app, lightweight, no dependencies, no pain but so much gain!
• Builds on top of collection views & table views, so you can easily mix and match.
• Does not replace Apple technologies with custom implementations, so you will always be safe and up-to-date, and you can easily revert at any time.
• Demo apps provided for macOS, iOS and tvOS (Kung Fu!)

Once, current document gets approved, will add so many enhancement for other array utilites also. This is my first document and need your assistance and approval in my effort.

Always remember the following mention from Apple.

In a horizontally compact environment, modal view controllers are always presented full-screen. In a horizontally regular environment, there are several different presentation options.