Top Most iOS Interview Questions

Q – 1 Explain what is iOS?

Ans- iOS is a mobile (i phone) operating system developed by Apple Inc. and distributed exclusively for Apple hardware. It is the operating system that powers many of the company’s i’Devices.

Q – 2 How to hide images in iOS?

Ans- Speaking of hiding images, if you want to hide one of your own just long tap the image and the Copy/Hide dialog pops up. Tap Hide and the image goes dark to show it has been hidden. You can still find it in the Hidden album, but no one else will see it.

Q – 3 How to delete images in iOS?

Ans- All deleted images are now kept for a period in the ‘Recently Deleted’ album. That’s handy if you ever delete things in error, but be sure to Delete All the images in that album if you happen to be a celebrity trying to keep intimate images from leaking online without your permission.

Q – 4 How to shut off message alerts in iOS?

Ans- Repeating message alert sounds getting you down? You can switch it off: Settings>Notifications>Messages Scroll to Repeat Alerts and flip this to Never. Now you will only be alerted once when new messages reach you.

Q – 5 How do I get a call when my iPad rings?

Ans- If you have multiple Apple devices that all use your Apple ID you may start to receive calls on all your devices at once. You can control this by switching off iPhone Cellular Calls in the Face-time section of each device’s Settings menu, but be sure to only disable this in devices you don’t want to use for calls.

Q – 6 How to silent the noisy keyboard?

Ans- If the clicks of your iOS 8 keyboard are driving you mad, switch it off in Settings>Sounds>Keyboard Clicks, toggle to off.

Q – 7 What is view object in iOS?

Ans- Views along with controls are used to provide visual representation of the app content. View is an object that draws content in a designated rectangular area and it responds to events within that area.

Q – 8 Do you know what are layer objects and what do they represent?

Ans- Layer objects are data objects which represent visual content. Layer objects are used by views to render their content. Custom layer objects can also be added to the interface to implement complex animations and other types of sophisticated visual effects.

Q – 9 How to switch off predictive text?

Ans- You can switch it off easily: Settings>General>Keyboard and toggle that switch to Off.

Q – 10 Who calls the main function of app during the app launch cycle in iOS?

Ans- During app launching, the system creates a main thread for the app and calls the app’s main function on that main thread. The Xcode project’s default main function hands over control to the UIKit framework, which takes care of initializing the app before it is run.

Q – 11 Explain app’s state transitions when it gets launched?

Ans- Before the launch of an app, it is said to be in not running state.
When an app is launched, it moves to the active or background state, after transitioning briefly through the inactive state.

Q – 12 How respond to state transitions on your app in iOS?

Ans- On state transitions can be responded to state changes in an appropriate way by calling corresponding methods on app’s delegate object.

Q – 13 Explain code signing in iOS?

Ans- Signing an application allows the system to identify who signed the application and to verify that the application has not been modified since it was signed. Signing is a requirement for submitting to the App Store (both for iOS and Mac apps).

OS X and iOS verify the signature of applications downloaded from the App Store to ensure that they they do not run applications with invalid signatures. This lets users trust that the application was signed by an Apple source and hasn’t been modified since it was signed.

Q – 14 What is suspended state in iOS?

Ans- The app is in the background but is not executing code. The system moves apps to this state automatically and does not notify them before doing so. While suspended, an app remains in memory but does not execute any code. When a low-memory condition occurs, the system may purge suspended apps without notice to make more space for the foreground app.

Q – 15 What is background state in iOS?

Ans- The app is in the background and executing code. Most apps enter this state briefly on their way to being suspended. However, an app that requests extra execution time may remain in this state for a period of time.

In addition, an app being launched directly into the background enters this state instead of the inactive state. For information about how to execute code while in the background, see “Background Execution and Multitasking.

Q – 16 What is active state in iOS?

Ans- The app is running in the foreground and is receiving events. This is the normal mode for foreground apps.

Q – 17 What is inactive state in iOS?

Ans- The app is running in the foreground but is currently not receiving events. (It may be executing other code though.) An app usually stays in this state only briefly as it transitions to a different state. The only time it stays inactive for any period of time is when the user locks the screen or the system prompts the user to respond to some event, such as an incoming phone call or SMS message.

Q – 18 What is the mean of not running State in iOS?

Ans- The app has not been launched or was running but was terminated by the system.

Q – 19 Can a “delegate” retained in iOS?

Ans- No, the delegate is never retained! Ever!

Q – 20 Can you please explain the difference between frame and bounds?

Ans- The frame of a view is the rectangle, expressed as a location (x,y) and size (width,height) relative to the super-view it is contained within. The bounds of a view is the rectangle, expressed as a location (x,y) and size (width,height) relative to its own coordinate system (0,0).

Q – 21 What is retain counts?

Ans- Retain counts are the way in which memory is managed in Objective-C. When you create an object, it has a retain count of 1. When you send an object a retain message, its retain count is incremented by 1. When you send an object a release message, its retain count is decremented by 1.

When you send an object a auto-release message, its retain count is decremented by 1 at some stage in the future. If an objectʼs retain count is reduced to 0, it is deallocated.

Q – 22 Can you please explain the difference between NSArray and NSMutableArray?

Ans- NSArrayʼs contents can not be modified once itʼs been created whereas a NSMutableArray can be modified as needed, i.e items can be added/removed from it.

Q – 23 What is struct?

Ans- A special C data type that encapsulates other pieces of data into a single cohesive unit. Like an object, but built into C.

Q – 24 Define fast enumeration?

Ans- Fast enumeration is a language feature that allows you to enumerate over the contents of a collection. (Your code will also run faster because the internal implementation reduces message send overhead and increases pipe-lining potential.)

Q – 25 Explain app bundle?

Ans- When you build your iOS app, Xcode packages it as a bundle. A bundle is a directory in the file system that groups related resources together in one place. An iOS app bundle contains the app executable file and supporting resource files such as app icons, image files, and localized content.

Q – 26 Explain iOS 7 AirDrop?

Ans- It does! AirDrop in iOS 7 lets you exchange files like pictures, Passbook passes, and contacts between two iOS users over Wi-Fi or Bluetooth, without any configuration and (as Apple’s Craig Federighi pointed out) without the need to walk around and “bump” phones with people.

AirDrop appears in the Share sheet, along with more conventional items like Mail and Messages; you can even use it to share multiple items to multiple people at once. Files end up right in the appropriate app and are encrypted during transmission. You can also change permissions to determine whether everybody can share with you, or only certain people nearby (or people in your contacts).

Q – 27 What are Moments and Collections?

Ans- For those of us that end up with thousands of pictures in our Camera Rolls, Moments and Collections offer a better way to organize those photos. Just as iPhoto on the Mac can automatically break pictures into events, Photos on iOS can use metadata like time and location to create different “Moments”-all the pictures you took on Thursday at dinner, for example, or all the photos you snapped while on that weekend trip to the country.

Collections are larger groupings of Moments-often all the photos you took in a general area (around your house) during a time period of often several months. Beyond that you can zoom out even further to a Years view that breaks down all the pictures you took in various (you guessed it) years.

Q – 28 What’s new with the iOS 7 Camera?

Ans- Like the rest of iOS 7, Camera’s gotten a significant overhaul. It offers four different modes: standard camera, video camera, a square camera, and panorama; you can swipe back and forth between them.

If you think that square camera might be Apple’s way of taking a shot at Instagram, congratulations: You’re spot on. The app also now includes different live photo filters that you can apply to your still or square shots. They’re even non-destructive, in case you want to remove them later.

Q – 29 Do you know any other changes to iOS 7 since WWDC?

Ans- There are new ringtones and alert options with iOS 7, if that’s the sort of thing that sets your pulse racing.

Q – 30 If any app can run in the background, what about battery life?

Ans- Apple’s spent a lot of time making sure that battery life won’t suffer from the new multitasking. It tries to collect updates from different apps and run them all at the same time, and keeps an eye on both power efficiency and the current network situation to make sure it doesn’t run down your battery.

Q – 31 How to access the Spotlight search feature now?

Ans- Very carefully. Spotlight’s moved from its traditional home on a separate home screen. With iOS 7, you’ll trigger searches by pulling from the center of the screen and essentially dragging your home screen downward. It’s a weird gesture to learn at first.

Q – 32 What devices will support iOS 7?

Ans- If you’re looking to update to iOS 7 when it lands in the fall, you’ll need to have one of these devices: the iPhone 4 or later; iPad 2 or later; iPad mini; or fifth-generation iPod touch. Oh, and both the iPhone 5s and iPhone 5c announced by Apple will arrive with iOS 7 already installed, though they don’t go on sale until September 20-two days after iOS 7’s release.

Specific features have more stringent device requirements (see below for details on these features):

Panoramic photos are only available on the iPhone 4S or later and fifth-generation iPod touch.
You can’t shoot square photos or video using the iPad 2; all other devices can use this feature, however.
For the nifty new live camera filters, you’ll need an iPhone 5 (including the s and c models) or fifth-generation iPod touch. Putting filters on after the fact in the Photos app is an option for the iPhone 4 or later, third-generation iPad or later, iPad mini, and fifth-generation iPod touch.

To AirDrop a photo or other file to your friends, you’ll need an iPhone 5 or later, fourth-generation iPad or later, iPad mini, or fifth-generation iPod touch. You’ll also need an iCloud account.

Siri continues to be limited to those using an iPhone 4S or later; third-generation iPad or later; iPad mini; and fifth-generation iPod touch. It also may not be available for your country. And if it’s a new Siri voice you desire, keep in mind that it’ll only be available initially in English, French, or German.

Q – 33 Will the new design mean I have to completely relearn how to use my phone?

Ans- Not really. Launching and using apps is largely the same. But there will be some new things to learn. For example, you can now swipe up from the bottom of the screen to summon Control Center (a handy panel that gives you access to many of your most commonly-used system features). There’s another new swipe-from-the-left-edge gesture that means “go up a level” when you’re in Mail, for example.

Q – 34 So how is the new look different from the old look?

Ans- How did you feel about green felt? Wood bookshelves? Stitched leather? I hope the answer is “not great,” because they’re all gone in iOS 7. Instead they’ve been replaced with a new cleaner design that’s largely about simple lines and icons.

While there are elements reminiscent of Microsoft’s recent Windows Phone design, iOS 7 clearly has its own distinct style. These aren’t just subtle enhancements either; they permeate every bit of the interface.

Q – 35 What is the biggest change with iOS 7?

Ans- Where to begin? The entire look and feel of the system has been overhauled, with flatter icons, less skeumorphism, and thinner typefaces. That said, anybody who’s used iOS will probably feel mostly at home: Apple hasn’t changed the home screen much, and the basic gestures and interactions are largely the same, with a few new exceptions.

Q – 36 What do you know about the iOS Kernel?

Ans- The iOS kernel is XNU, the kernel of Darwin. The original iPhone OS (1.0) up to iPhone OS 3.1.3 used Darwin 9.0.0d1. iOS 4 was based on Darwin 10.0.0. iOS 5 was based on Darwin 11.0.0. iOS 6 was based on Darwin 13.0.0. iOS 7 is based on Darwin 14.0.0

Q – 37 Explain iOS Switching applications?

Ans- In iOS 4.0 to iOS 6.x, double-clicking the home button activates the application switcher. A scrollable dock-like interface appears from the bottom, moving the contents of the screen up. Choosing an icon switches to an application. To the far left are icons which function as music controls, a rotation lock, and on iOS 4.2 and above, a volume controller.

Holding the icons briefly makes them “jiggle” (similarly to the homescreen) and allows the user to force quit the applications by simply tapping the red minus circle that appears at the corner of the app’s icon.

Q – 38 Explain iOS multitasking?
Ans- multitasking is supported through seven background APIs:

Background audio – application continues to run in the background as long as it is playing audio or video content
Voice over IP – application is suspended when a phone call is not in progress
Background location – application is notified of location changes
Push notifications
Local notifications – application schedules local notifications to be delivered at a predetermined time
Task completion – application asks the system for extra time to complete a given task
Fast app switching – application does not execute any code and may be removed from memory at any time

Q – 39 What do you know about Home Screen of iOS?

Ans- The home screen (rendered by and also known as “SpringBoard”) displays application icons and a dock at the bottom of the screen where users can pin their most frequently used apps.

The home screen appears whenever the user unlocks the device or presses the “Home” button (a physical button on the device) whilst in another app. The screen’s background can be customized with other customizations available through jailbreaking.

The screen has a status bar across the top to display data, such as time, battery level, and signal strength. The rest of the screen is devoted to the current application. When a passcode is set and a user switches on the device, the passcode must be entered at the Lock Screen before access to the Home Screen is granted.

Q – 40 Can we use SSL to encrypt the App communication?

Ans- Yes. On WordPress.com blogs, all communication (done over XML-RPC) is by default going to use an encrypted connection via SSL. For self-hosted WordPress, if you have SSL enabled, WordPress 2.6.1 or later supports pointing the RSD information at the “https” version of xmlrpc.php which creates an encrypted communication link with the App.

Q – 41 Can we save posts to local drafts and figure out how to publish to the blog. what do we need to do?

Ans- When you are ready to publish, change the status of the post (from the Settings screen) to “Published” and then tap “Save.”

Q – 42 Can we adjust the size of photos uploaded from the app?

Ans- You can choose whether to have photos resized for faster uploading. You can choose between predefined dimensions (small/medium/large) or setting a custom resize dimension.

Q – 43 Suppose I get a “Blog returned invalid data” error message. What do I do?

Ans-

1. A common issue that can cause errors with the App is invalid characters. The easiest way to check is to go to the W3C Markup Validator and type in the URL of your WordPress site. If you get a response such as “… one or more bytes that I cannot interpret as UTF-8″ that is most likely what is causing the app to have trouble with your site.

2. You can also try with the default theme and with no active plug-in.
(Trying it with the default theme and plugins disabled will help pin down where the problem is. If everything works then you go back and enable your theme and then try it again. If everything still works then you go back and activate each plugin one at a time until you find the one that is causing the breakage.)

Q – 44 Which devices will this work with iOS?

Ans- The App works with any device that is running iOS version 7 or greater.