Objective C test answers of 2016.

In this post you can find Complete and recently updated Correct Question and answers of Objective C. All Answers updated regularly with new questions. Upwork Objective C test answers of 2016.

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Question:* What is a pointer?

Answer: • A memory address that points to a specific object

Question:* What is the difference between #import and #include ?

Answer: • #import ensures that a file is only ever included once, and #include allows the same file to be inlcuded many times.

Question:* How do you get the Unicode character set of a Core Text font?

Answer: • CTFontCopyCharacterSet

Question:* What is the method for adding KVO to your app?

Answer: • addObserver:forKeyPath:options:context

Question:* How can you declare a method, that can be set as the action to be performed on various events?

Answer: • - (IBAction) action:(id) sender;

Question:* What is a design pattern?

Answer: • A template for a solution to a common problem faced by programmers.

Question:* True or False? For an object to use constraints, it must have at least 3 constraint values.

Answer: • False

Question:* Does Objective-C have constructors and destructors?

Answer: • No, you use init and dealloc on Objective-C

Question:* What framework is KVO (key value observing) a part of?

Answer: • Foundation

Question:* If you do not declare a return type for a method definition, what is the default return type?

Answer: • id

Question:* What class supports the sharing of small amounts of data such as strings or dates to iCloud?

Answer: • NSUbiquitousKeyValueStore

Question:* Assume ARC is enabled... What would be another way to write this: NSArray *array = [NSArray arrayWithObjects:@"One", @"Two", @"Three",nil];

Answer: • NSArray *array = @[@"One", @"Two", @"Three"];

Question:* What is the type of @selector(foo)?

Answer: • SEL

Question:* Using UIViewController containment, which one of the following statements is true:

Answer: • The root viewcontroller handles loading and unloading its child viewcontrollers.

Question:* what does this code produce? [NSString] *myString = @"Hello World";

Answer: • An Error during compile

Question:* Can you call C++ code from objective C environment?

Answer: • Yes, from any .mm file

Question:* What is a dependency in NSOperationQueue?

Answer: • A dependency is a way to have an operation wait to be performed until the dependencies have been fulfilled/executed

Question:* If a class conforms to a protocol what must it do?

Answer: • Implement all methods in the protocol, except for optional ones

Question:* Which of the following accesses a variable in structure b?

Answer: • b.var;

Question:* How can you add a new method foo to an existing class Bar?

Answer: • Make a category, e.g. @interface Bar(Foo).

Question:* True or False? Sending a command asynchronously will lock the main thread and then wait until the command is finished before moving on to the next part of your code.

Answer: • False

Question:* What is KVO?

Answer: • Key Value Observing

Question:* What is a Category?

Answer: • A category is a way to extend a class by adding functions to it

Question:* True or False? A method and a variable can have the same name in Objective-C.

Answer: • True

Question:* How does KVO respond to change notifications?

Answer: • observeValueForKeyPath:ofObject:change:context

Question:* What is the Allocations instrument used for?

Answer: • Recording information from a single process about memory allocation

Question:* What is used to sort Core Data results?

Answer: • NSSortDescriptor

Question:* True or False? You can compare two strings by (string1 == string2)

Answer: • False

Question:* What is the difference between methods that begin with + and -?

Answer: • Instance methods begin with - class level methods begin with +

Question:* What does a CAEmitterCell do?

Answer: • It defines the properties and direction of emitted particles from a CAEmitterLayer object.

Question:* What happens when you call retain on an object?

Answer: • You increase its retain count by 1

Question:* What type of object is this under XCode 4.5: @[rabbit, chicken, owl]

Answer: • NSArray

Question:* How do you free an object?

Answer: • [obj release]

Question:* True or False? A UIButton inherits from UIView.

Answer: • True

Question:* What does the "id" type mean?

Answer: • This is the general type for any kind of object regardless of class

Question:* Which of the following is a Singleton?

Answer: • [NSFileManager defaultManager]

Question:* How do you concatenate two NSStrings *foo and NSString *bar to form a new NSString *baz?

Answer: • baz = [foo stringByAppendingString: bar];

Question:* What framework does the class UIButton come from?

Answer: • UIKit

Question:* Are integers full-fledged objects in Objective-C?

Answer: • No, they are not objects at all.

Question:* What does an Objective-C string literal look like?

Answer: • @"foo"

Question:* If you define a new class called Foo which inherits from NSObject, how do you create a new instance of it?

Answer: • Foo *temp = [[Foo alloc] init];

Question:* ARC means?

Answer: • Artificial Reference Counting

Question:* Where is a MKAnnotationView used?

Answer: • On a Map View

Question:* What is a delegate?

Answer: • A delegate allows one NSObject to send messages to another NSObject, and listen to those messages

Question:* What is the name of the type of SQL Database that iOS Supports?

Answer: • SQLite

Question:* What is one source of particles that are emitted by a CAEmitterLayer object?

Answer: • A CAEmitterCell

Question:* In Core Data, what is the name of an object representation of a record?

Answer: • NSManagedObject

Question:* True or False? You should use NSHost when connecting to a specific host.

Answer: • False (You should use CFHost)

Question:* What happens at runtime with the following: NSObject* object = nil; NSObject* object2 = [object copy]; NSLog(@"%@", object2);

Answer: • Log prints "(null)" and continues as usual.

Question:* True or False? You can perform operator overloading in Objective-C.

Answer: • False

Question:* True or False? Strings are one of the most common sources of buffer overflow attacks.

Answer: • True

Question:* What class will allow you to use one or more blocks concurrently?

Answer: • NSBlockOperation

Question:* What is the 'print object' command in the debugger window?

Answer: • po

Question:* The proper typedef syntax for an Objective-C block that takes an NSArray and returns an NSString is

Answer: • typedef NSString *(^aBlock)(NSArray *);

Question:* What is a persistent object store?

Answer: • It represents an external file of persisted data

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

Answer: • None, they perform the same actions.

Question:* What is a proper format for calling an asynchronous function?

Answer: • dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0), ^{ // code });

Question:* What are the two types of predicates?

Answer: • Comparison and Compound

Question:* What is Objective-C's language design based on?

Answer: • C and Smalltalk.

Question:* True or False? You can use %@ to specify a dynamic property.

Answer: • False

Question:* How do you convert a Core Image color to a UIColor?

Answer: • colorWithCIColor:

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

Answer: • NSManagedObjectModel

Question:* What can happen if you use self inside a block?

Answer: • You can create a retain cycle

Question:* Objective-C methods with certain names (“init”, “alloc”, etc.) always return objects that are an instance of the receiving class’s type; such methods are said to have a “related result type”. A method with a related result type can be declared by using:

Answer: • instancetype

Question:* True or False? The format for a NSPredicate is the same as a Regular Expression.

Answer: • False

Question:* What protocol is used to create an action object?

Answer: • CAAction

Question:* What is the object.toString equivalent in objective-c?

Answer: • [NSObject description]

Question:* How can you temporarily disable layer actions in a Core Animation?

Answer: • Using the CATransaction class

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

Answer: • NSKeyedUnarchiver unarchiveObjectWithData:

Question:* What is (void*)0 ?

Answer: • Representation of NULL pointer

Question:* Which of these property declaration attributes does not specify setter semantics?

Answer: • nonatomic

Question:* Which of these classes is NOT a root class?

Answer: • NSString

Question:* What does the following code do, assume ARC is enabled? NSArray *myArray; for (int i = 0; i < 10; i++){ @autoreleasepool { myArray = [[NSArray alloc]init]; } }

Answer: • For each iteration of the loop a new array is allocated and released.

Question:* True or False? Key value coding is used to indirectly access an object's attributes using indexes.

Answer: • False

Question:* If you wanted to override the default alloc method in a class Foo, what would be the appropriate way to declare it?

Answer: • + (id) alloc;

Question:* What do you use for an outgoing TCP connection?

Answer: • NSStream

Question:* What happens if you use fgets and do not give it a size smaller than the buffer?

Answer: • It will overwrite the data past the size

Question:* What can you say about the code: NSString * str = [NSString stringWithFormat:@""]; [str release];

Answer: • It will cause the string to be released twice with undefined consequences when the surrounding autorelease pool is emptied

Question:* How do you add a brightening effect on a CoreImage?

Answer: • CIAdditionCompositing

Question:* Which method, if defined, is guaranteed to be called once -- and only once -- when a class is first referenced?

Answer: • + (void) initialize;

Question:* Which of these methods is NOT invoked by the runtime itself?

Answer: • -dealloc

Question:* What is the last chance for an object to handle a message?

Answer: • -forwardInvocation:

Question:* How is a selector typically represented in memory?

Answer: • As a null terminated C string.

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