IOS Interview Questions

IOS Interview Questions

Whether you are a candidate or an interviewer you may always find it difficult to lay hands on the best kind of questions for an interview, especially such an important one. iOS interview questions are all technology-based that is very straightforward if you have the basic idea of what you are dealing with. Any amount of preparation is a waste of time if you are not through with the basics. Here is a list of important questions that will refresh your brain to prepare for the iOS interview.

The questions will give you an idea about the pattern and the right way to answer the questions that may be thrown your way during the interview. So, without adieu lets' start with the questions and answers that may come in the iOS interview.

Read Few Important iOS interview questions and answers

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IOS Interview Questions

The QuickTime Player on Yosemite cannot record encrypted media by the HTTP Live Streams during screen recording. As a result, these will simply black out in the recorded video.

The HTTP Live Streaming tech (HLS) from Apple allows you to send and receive on-demand and live video and audio media on your iPad, iPhone, Apple TV, Mac and PC. HLS uses the very same properties and procedures which drive the web and thus, lets the user make use of content with the help of ordinary content delivery networks and web servers. HLS is exclusively designed for high reliability and it dynamically modifies itself to suit the network conditions. This is done by optimization of playback according to the available connection speed offered by wired or wireless devices.

 A managed object context is a provisional ‘scratchpad’ of sorts in any application for a collection or set of related objects. It is represented generally by an instance of the method NSManagedObjectContext( ). These related objects together represent a consistent view from the inside of one or even more persistent stores.
  • Multiple copies of any object could exist in various contexts but a singular instance of the managed object exists in not more than one context.

The chief functions of a managed object context comprise of the following:

  • Management of life cycle: In this case, the context delivers proof, undo/redo and handling of the inverse relationship.
  • Notifications: These denote the context posts notices at different points which can be observed from another part of the application.
  • Concurrency: When the Core Data makes use of confinement of threads or serialized queues in order to protect the managed object contexts and the managed objects too.
When Apple brought iOS 9, with it was introduced the NSLayoutAnchor class to that made writing auto-layout easier with the code.

There are three subclasses of NSLayoutAnchor:

  • NSLayoutYAxisAnchor This subclass is used to create vertical constraints
  • NSLayoutDimension This subclass is used to create the width and height constraints
  • NSLayoutXAxisAnchor This subclass is used to create horizontal constraints
URL session can be used to download an image as data and then it can be converted into UIImage from NSData. After that, we need to connect it UIImageView IBOutlet. A much better way is by using a library. With the help of built-in connectivity monitoring and URLSession Adaptable Connectivity API, we can run a request, in case of no connection. The request will download after waiting whenever the resource is available instead of failing.
Open Authorization is often referred to as OAuth, which is generally an authorization protocol and not used for authentication. As OAuth is an authorization protocol, it is just concerned with authorization of third-party application that can be used to access user data without identifying the user or exposing its credentials. It has two libraries namely, OAuth2 and OAuthSwift
Absolutely no, the private method in Object-C programming is not a method. The method becomes protected only when it is defined in .m. If a method is in .h, then it becomes public.
If you are really looking for a private method then you will have to add an unnamed category /local category/class extension in the class and add the method in the category and define it in the class.m.
The IGListKit is known to provide for different objects automatically that can be used to create deletions, moves, and insertions before it starts performing the batch updates on collection view. If a user happens to delete an update, which is in the queue that is being viewed, then we make sure that it fades out without the requirement of pulling down to refresh.
This way we can say goodbye to UICollectionViewDatasource, instead, we can use an IGListAdapterDataSource with IGListAdapter. The data source provides the array of Selection Controllers and doesn’t return counts or cells.
The Section Controllers are used to control cells and configure within the given collection view section.
The Main Thread Checker is a new tool launched with Xcode 9 is Main thread checker, which detects the invalid use of Apple’s frameworks like AppKit, UIKit, etc., that supposed to be used from main thread but accidentally used in the background thread. The effect of the invalid usage can result in missed visual defects, UI updates, crashes, and data corruption.
For iOS and macOS, Alamofire is a networking library, which is based on HTTP Swift. It is known to provide an elegant interface to simplify a lot of common tasks of networking, on top of Apple’s Foundation networking stack.
  • AlamoFire is needed to create a route, which means that if we create request then it can be executed to the server by one static function.
  • It can provide methods for chaining for the request that is returned. This makes it easy for adding handling responses and headers.
  • It also has the number of response handlers, which is generally returned in parse JSON, text, binary form, and even multiple of each can be used for a given request.
  • AlamoFire also has a method for chaining that allows response validation. We can call validation to check for the status code of the HTTP response, the content type, or any custom validation you might need to do for our app.
  • AlamoFire gives a couple of URLRequestConvertible, protocols, and URLConvertible. These protocols can be passed on while creating a request.
  • AlamoFire is known to provide extensions that can be passed on to create the request.
Properties which are stated as atomic are those which always return, with certainty, fully initialized object. The atomic property is also the default specification for all synthesized properties. It is generally good to specify them as atomic in order to completely remove the odds for confusion. However, this guarantee by atomic properties comes at the expense of performance. But in the case of properties which do not offer risks while retrieving any uninitialized value, setting them to non-atomic properties can actually boost the performance. An example of this is the case where all accesses to the particular property are synced through other means in advance.
The major difference between MKAnnotation and MKPointAnnotation is that MKAnnotation is a protocol whereas MKPointAnnotation is a class that implements MKAnnotation. MKAnnotation protocol is implemented by NSOject subclass that is created by us. Instances of this custom class will then serve as your map annotation.

We can use MKPointAnnotation directly if we want our own business logic on the annotation.

The process of data conversion into a single JSON or string is called Serialization. It can be transmitted or stored easily. Another word for Serialization is encoding. A single string when through the reversible process is turned into a data is known as deserialization or decoding.
In swift we use the Codable protocol that a type can conform to, to declare that it can be encoded and decoded. It’s basically an alias for the Encodable and Decodable protocols.

Our code takes up some space in the iOS. The size of this is sometimes fixed and sometimes it can change according to what the user will enter during the program. Basically, we have two different methods because of this difference: Stack and Heap.

A stack is used and automatically removes itself from memory after work is finished. But in Heap, the user could do it by writing manual code for deleting from memory.

Stack:Heap
• A stack is easy to use.• Compared to Stack, it is quite slow.
• It’s kept in RAM on the computer.• It creates memory problems if not used correctly.
• Created variables are automatically deleted when they exit the stack.• Variables are used with pointers.
• It is quite fast compared to Heap.• It is created at runtime.
• Constructed variables can be used without a pointer. 
A user can state changes in the most apt way in order to respond to the state transitions. Calling the corresponding methods or functions on the app’s delegate object is one way of doing this.

For instance:

  • The method applicationDidBecomeActive( ) can be employed to arrange the app to run as the fore app.
  • The method applicationDidEnterBackground( ) can be employed for the execution of some code during the background runtime of the app and the exercise may be put on hold at any time.
  • The method applicationWillEnterForeground( ) can be employed when the app is moving into the foreground and shifting out of background and some code needs to be executed.
  • The method applicationWillTerminate( ) is called to action when the app is nearing termination.
While scrolling a scrollView the properties may get modified in the process and it is known as content offset. The scrollView can compute the new bounds and redraw any of its subviews. It is a point at which the origin of the contentView, i.e., the bounds rectangle, is offset from the origin of the scrollView.