Multiple option interview questions

What is the first method called in the iOS App initialisation flow? & what is the return type?

• Main, , Return the is void.
• App Delegate, Return type is Bool
• UIApplicationMain, Return type is Bool
• Main, Return type is int.

What is the parent class of App Delegate?

• UIResponder
• NSObject
• UIApplicationMain
• UIKit

What is the difference between [Foo new] and [[Foo alloc] init]?

• New will not always initialize the object.
• New is significantly faster than alloc + init.
• None, they perform the same actions.
• New does not exist in Objective-C.

What happens at runtime with the following :

    NSObject *obj1 = nil;

    NSObject *obj2 = [obj1 copy];

    NSLog(@"value of object 2  %@",obj2);

• Application crashes with “SIGABRT”
• Application continues, but issues “cannot access nil object reference” warning
• Object 2 is instantiated as an NSObject with nil Values
• Log prints “(null)” and continues as usual

What is the object.toString equivalent in Objective-C?

• [NSObject toString];
•  [NSObject description];
• [NSObject stringWithFormat];
•  [NSObject getDescription];

The format for a NSPredicate is the same as a Regular Expression

• True
• False

What can happen if you use “self” inside a block?

• None of the above.
• Self can become dangling pointer.
• You can create a retain cycle.
• By the time the block executes, self can be pointing to a different object[NSObject toString]

What is @dynamic directive meaning in iOS?

• The @dynamic directive generates the accessor methods for you at compile time.
• The @dynamic directive tells the compiler that you will provide accessor methods dynamically at runtime.
• The @dynamic directive generates a getter method for your property at compile time.
• The @dynamic directive generates a getter method for your property at run time.

You can use %@ to specify a dynamic property

• True
• False

What is difference between #import and #include?

• #import ensures that a file is only ever included once, and #include allows the same thing.
• None, they do the same thing.
• #include is not valid syntax.
• #include ensures that a file is only ever included once and #import permits the file to be included many times.

A UIView is a superclass of:

• UIViewController
• UIWindow
• UIImage
• UILabel
• UIScreen

A method and a variable can have the same name in Objective C.

• True
• False

What framework is KVO (Key Value Observing) a part of?

• Foundation
• UIKit
• CoreData
• UIKItCore

What class method is used to make an NSArray from NSData class?

• NSArray arrayWithObject:
• NSArray dataWithContentsOfFile:
• NSData dataWithContentsOfFile:
• NSKeydUnarchiver unarchiveObjectWithData:

In Core Data, what is the name of the object representation for the database schema?

• NSManageObjectContext
• NSManagedObjectModel
• NSEntityDescription
• NSManagedObject

What’s the difference between “nil” and “NULL” ?

• nil is a literal null value for Objective-C instances. NULL is object used to represent null.
•  nil is a literal null value for Objective-C instances. NULL is literal null value for Objective-C classes.
• Nil is a literal null value for Objective-C instances. NULL is literal null value for C pointers.
• NULL is literal null value for Objective-C instances. Nil is literal null value for C pointers
• they are the same thing

Which of the following is Singleton class?

• NSFileManager
• UIApplication
• NSFileManger & UIApplication
• NSArray & NSDictionary
• NSString & NSOperations

What is the output of the below program?

    NSMutableString *tempString = [NSMutableString stringWithString:@"1"];

    dispatch_async(dispatch_get_main_queue(), ^{

        [tempString appendString:@"2"];

        NSLog(@"%@",tempString);

    });

    [tempString appendString:@"3"];

    NSLog(@"%@",tempString);

• Log prints “13” & “132” and continues as usual.
• Log prints “12” and then we will have a deadlock here because the main queue will block.
• Log prints “123” and continues as usual.
•  Log doesn’t print anything. It’s deadlock here because the main queue will block on the call to dispatch_async.

What is the output of the below program?

    NSMutableString *tempString = [NSMutableString stringWithString:@"1"];

    dispatch_sync(dispatch_get_main_queue(), ^{

        [tempString appendString:@"2"];

        NSLog(@"%@",tempString);

    });

    [tempString appendString:@"3"];

    NSLog(@"%@",tempString);

• Log prints “13” & “132” and continues as usual.
• Log prints “12” and then we will have a deadlock here because the main queue will block.
• Log prints “123” and continues as usual.
•  Log doesn’t print anything. It’s deadlock here because the main queue will block on the call to dispatch_async.

What is used to sort Core Data results?

• NSSort
• NSCoreDataSort
• [self sort]
• NSSortDescriptor
• NSPredicate

Note : Answer is written in Bold.