ios interview questions

Top ios frequently asked interview questions

Do Swift-based applications work on OS X 10.9/iOS 7 and lower?

Will Swift-based applications work on OS X 10.9 (Mavericks)/iOS 7 and lower?

For example, I have a machine running OS X 10.8 (Mountain Lion), and I am wondering if an application I write in Swift will run on it.

Source: (StackOverflow)

How to develop or migrate apps for iPhone 5 screen resolution?

The new iPhone 5 display has a new aspect ratio and a new resolution (640 x 1136 pixels).

What is required to develop new or transition already existing applications to the new screen size?

What should we keep in mind to make applications "universal" for both the older displays and the new widescreen aspect ratio?

Source: (StackOverflow)

Codesign error: Provisioning profile cannot be found after deleting expired profile

Tried to rebuild an app that was just working yesterday. Got a message that a profile had expired, so I removed it from the iPod and from iTunes. When I chose a new profile (one with an * in the identifier), I now get an error:

Code Sign Error: Provisioning Profile (long string) can't be found.

What am I missing? I looked through related questions and didn't see this scenario already. Thanks

Source: (StackOverflow)

Can I embed a custom font in an iPhone application?

This question relates to iOS pre-3.2. As of 3.2 this functionality is easily achievable using samvermette's answer below, and I have changed the Accepted Answer (from commanda to samvermette) to reflect this. I can't give credit to both answers (besides uproots) but they are both good.

I would like to have an app include a custom font for rendering text, load it, and then use it with standard UIKit elements like UILabel. Is this possible?

I found these links:

but these would require me to render each glyph myself, which is a bit too much like hard work, especially for multi-line text.

I've also found posts that say straight out that it's not possible, but without justification, so I'm looking for a definitive answer.

EDIT - failed -[UIFont fontWithName:size:] experiment

I downloaded Harrowprint.tff (downloaded from here) and added it to my Resources directory and to the project. I then tried this code:

UIFont* font = [UIFont fontWithName:@"Harrowprint" size:20];

which resulted in an exception being thrown. Looking at the TTF file in Finder confirmed that the font name was Harrowprint.

EDIT - there have been a number of replies so far which tell me to read the documentation on X or Y. I've experimented extensively with all of these, and got nowhere. In one case, X turned out to be relevant only on OS X, not on iPhone. Consequently I am setting a bounty for this question, and I will award the bounty to the first person who provides an answer (using only documented APIs) who responds with sufficient information to get this working on the device. Working on the simulator too would be a bonus.

EDIT - It appears that the bounty auto-awards to the answer with the highest number of votes. Interesting. No one actually provided an answer that solved the question as asked - the solution that involves coding your own UILabel subclass doesn't support word-wrap, which is an essential feature for me - though I guess I could extend it to do so.

Source: (StackOverflow)

Using Auto Layout in UITableView for dynamic cell layouts & variable row heights

How do you use Auto Layout within UITableViewCells in a table view to let each cell's content and subviews determine the row height, while maintaining smooth scrolling performance?

Source: (StackOverflow)

Version vs build in XCode

I have an app that I developed with XCode 3 and recently started editing with XCode 4. In the target summary I have the iOS application target form with fields: identifier, version, build, devices, and deployment target. The version field is blank and the build field is 3.4.0 (which matches the version of the app from when I was still editing with XCode 3).

My questions are:

  1. What is the difference between the version and build fields?

  2. Why was the version field blank after I upgraded to XCode 4?


Source: (StackOverflow)

Xcode process launch failed: Security

I've been developing an app for 1 or 2 weeks now and just yesterday I've updated my iPhone 5S to the iOS 8 GM. Everything worked fine and I could test on my device as well until I deleted the app from my phone and wanted to build again. The following error appeared:

Could not launch "My App"
process launch failed: Security

When I test with the simulator it works fine. Is this because of the iOS 8 GM update and how can I fix this launch problem? I want to be able to test on my iPhone and in the simulator.

Source: (StackOverflow)

What does this mean? "'NSUnknownKeyException', reason: ... This class is not key value coding-compliant for the key X"

I'm trying to link a UILabel with an IBOutlet created in my class.

My application is crashing with the following error. What does this mean? How can I fix it?

*** Terminating app due to uncaught exception 'NSUnknownKeyException', reason: '[<UIViewController 0x6e36ae0> setValue:forUndefinedKey:]: this class is not key value coding-compliant for the key XXX.'

Source: (StackOverflow)

How do you trigger a block after a delay, like -performSelector:withObject:afterDelay:?

Is there a way to call a block with a primitive parameter after a delay, like using performSelector:withObject:afterDelay: but with an argument like int/double/float?

Source: (StackOverflow)

Transport Security has Blocked a cleartext HTTP

What setting do i need to put in my info.plist to enable http mode as per the error message:

Transport security has blocked a cleartext HTTP (http://) resource load since it is insecure. Temporary exceptions can be configured via your app's Info.plist file.

Source: (StackOverflow)

How do I test if a string is empty in Objective C?

How do I test if an NSString is empty in Objective C?

Source: (StackOverflow)

How do I create delegates in Objective-C?

I know how delegates work, and I know how I can use them.

But how do I create them?

Source: (StackOverflow)

How to check iOS version?

I want to check if the iOS version of the device is greater than 3.1.3 I tried things like:

[[UIDevice currentDevice].systemVersion floatValue]

but it does not work, I just want a:

if (version > 3.1.3) { }

How can I achieve this?

Source: (StackOverflow)

How can I disable the UITableView selection highlighting?

When you tap a row in a UITableView, the row is highlighted and selected. Is it possible to disable this so tapping a row does nothing?

Source: (StackOverflow)

Passing Data between View Controllers

I'm new to iOS and, Objective-C and the whole MVC paradigm and I'm stuck with the following:

I have a view that acts as a data entry form and I want to give the user the option to select multiple products. The products are listed on another view with a UITableView controller and I have enabled multiple selections.

My question is, how do I transfer the data from one view to another? I will be holding the selections on the UITableView in an array, but how do I then pass that back to the previous data entry form view so it can be saved along with the other data to core data on submission of the form?

I have surfed around and seen some people declare an array in the app delegate. I read something about Singletons but don't understand what these are and I read something about creating a data model.

What would be the correct way of performing this and how would I go about it?

Source: (StackOverflow)