Objective C - LinkedIn Skill Assessments Quizzes with Answers


Q1. What is the value of s?

NSMutableString *s = [NSMutableString stringWithString: @"123"];
[s appendString: @"456"];
  • 123456
  • 123
  • 456
  • This code contains an error.

Q2. What’s the value of i after these statements?

NSString *str = nil;
NSInteger i = str.integerValue;
  • nil
  • 0 (technically nil == 0 but i will have a literal value of 0 and not the void* value of nil)
  • -1
  • This code crashes.

Q3. What value is in str after this line in executed?

NSString str = "test" + " " + "more";

  • This code contains an error
  • test
  • nil
  • test more

Q4. What does this code print?

    NSPredicate *p2 = [NSPredicate predicateWithBlock:^BOOL(NSString*  evaluatedObject, NSDictionary<NSString *,id> * _Nullable bindings) {
      return evaluatedObject.intValue % 2 == 0;
    NSArray *vals = @[@"1", @"2", @"3"];
    NSArray *n2 = [vals filteredArrayUsingPredicate:p2];
    NSLog(@"%@", n2.firstObject);
  • 2
  • 1,2,3
  • 1,2
  • Nothing, since this code contains an error.

Q5. Property defaults include _?

  • atomic/strong
  • atomic/weak
  • nonatomic/weak
  • nonatomic/strong

Q6. What is the key difference between NSDictionary and NSMutableDictionary?

  • NSMutableDictionary’s values can change
  • NSMutableDictionary has not initializers.
  • NSDictionary can’t be copied.
  • NSDictionary’s values can change.

Q7. What is foo?


  • A function with a return type of float.
  • This code contains an error.
  • A variable declaration of type float.
  • A property of type float.

Q8. What can you glean from this line?

#import "NSString+NameHelper.h"

  • NameHelper is a category of NSString.
  • NameHelper is a subclass of NSString.
  • NSString implements the NameHelper protocol.
  • NSString has a helper class.

Q9. What’s wrong with this code?

float x = 5.;

  • Nothing is wrong with this code.
  • Declarations do not need semicolons.
  • x=5 is an invalid float.
  • Variables can’t be declared and initialized in the same state.

Q10. How many times with this loop be executed?

for (int x=0; x<100; x++) {
  x = x + 1;
  • 50
  • 99
  • 100
  • This code contains an error.

Q11. What is this code an example of?

[self addObserver: self forKeyPath: @"val" options:0 context: nil];

  • Key-Value Observing
  • Class Value Observing
  • Key-Data Observing
  • KeyPath Observing

Q12. What does ARC stand for?

  • Automatic Reference Counting
  • Automatic Retain Checking
  • Async Retain Cycles
  • Automatic Release Code

Q13. What is printed for this code?

int val = 0;
val = 1.5;
printf("%d", val);
  • 1
  • 2
  • 0
  • This code contains an error.

Q14. What best describes class inheritance in Objective-C?

  • single inheritance but multiple protocol implementation
  • Objective-C doesn’t support inheritance
  • dual class inheritance
  • unlimited class inheritance and protocol adherence

Q15. How many keys does this NSDictionary have after this code is executed?

NSDictionary *dict = [[NSDictionary alloc] initWithObjectsAndKeys: @"b", @"e", @"a", @"r", nil];

  • 2
  • 4
  • 5
  • This code contains an error.

Q16. What is wrong with this code?

NSMutableDictionary *dict1 = [NSMutableDictionary dictionaryWithCapacity:5];
[dict1 setValue:@"key" forKey:@"value"];
  • The key and value items are mixed
  • Nothing is wrong with it
  • You can’t set the capacity of a dictionary
  • NSMutableDictionary doesn’t have a :setValue:forKey function.

Q17. What is printed from this code?

NSData *data = [@"print" dataUsingEncoding:NSASCIIStringEncoding];
NSLog(@"%@", [[NSString alloc] initWithData:data encoding:NSASCIIStringEncoding]);
  • print
  • This code is invalid
  • Nothing is printed from this code.
  • nil

Q18. What is different about this function?


  • It is static
  • It is abstract.
  • It is inline.
  • This code contains an error.

Q19. Structs can have _?

  • functions
  • initializers
  • fields
  • all of these answers

Q20. What is wrong with this code?

@interface MyClass : NSObject
    @property (strong, nonatomic, readonly) NSString *name;
  • There is nothing wrong with this code.
  • There is not read-only directive.
  • MyClass doesn’t implement NSObject.
  • Properties are declared in the implementation.

Q21. What is an enums base type for the code below?

typedef enum { Foo1, Foo2} Foo;

  • There is no base type.
  • NSObject
  • int
  • NSNumber

Q22. If you want to store a small amount of information (e.g., user settings), whats the best, built-in way to go?

  • UserDefaults
  • plist file
  • CoreData
  • TextFile

Q23. What are categories used for?

  • to extend other classes
  • to manage access control
  • to coordinate objects
  • to group classes

Q24. What is this Objective-C code checking?

if ([keyPath isInstanceOf:[NSString class]]) {
  • This code contains an error
  • if keyPath is an instance of NSString
  • if keyPath’s baseclass is the same as NSString’s baseclass
  • if keyPath implements the same methods as NSString

Q25. What is this a declaration of?


  • an Extension
  • a Generic
  • a block of code
  • an abstract class
1. _val = 1;
2. self.val= 100;
  • Statement 2, since it calls the auto-created setter on the property.
  • Statement 1, since it uses the property directly.
  • Statement 2, since it specifies the class instance to use.
  • Statement 1, since it calls the auto-created setter on the property.

Q27. What is wrong with this code?

float x = 2.0;
int(^foo)(int) = ^(int n1) {
  return (int)(n1*x);
  • Ints and floats can’t be multiplied.
  • The parameter isn’t declared correctly.
  • x is not in the right scope.
  • Nothing is wrong with this code.

Q28. What’s the difference between an array and a set?

  • Arrays are ordered, non-unique values.
  • Arrays are stored sorted.
  • Sets are ordered, unique values.
  • Sets can contain nils.

Q29. Dot notation can be used for _?

  • nothing, as they’re never used in Objective-C
  • function calls only
  • property getter/setter
  • parameter delimiters

Q30. What is the value of newVals after this code is executed?

    NSArray *vals = @[@"1", @"2", @"3"];
    NSPredicate *pred = [NSPredicate predicateWithFormat:@"SELF.intValue > 1"];
    NSArray *newVals = [vals filteredArrayUsingPredicate:pred];
  • 2,3
  • nil
  • This code contains an error
  • 2,“3”

Q31. How would this function be called?

-(int)foo:(int)a b:(int)c;

  • self.foo(5, b:10);
  • This code contains an error.
  • [self foo:5:10:20];
  • [self foo:5 b:10];

Q32. What is the type of the error return value stored in json?

    NSError *error;
    NSData *data;
    id json = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingAllowFragments error:&error];
  • NSString
  • NSArray
  • id
  • NSDictionary

Q33. What is significant about this function declaration?

  • The parameter is passed by value and can not be changed
  • ** is not allowed on a parameter
  • The parameter may be nil
  • The parameter is passed by reference and may be changed

Q34. What is printed from this code execution?

    typedef enum {
    } Thing;

    -(void) enumStuff {
        NSLog(@"%d", thing2);
  • 0
  • 1
  • thing2
  • This code does not print anything

Q35. You are worried about threaded access to a property and possible collision in writing. What directive should you use on the property?

  • non-atomic
  • strong
  • weak
  • atomic

Q36. What is wrong with this line of code?

int temp = 1==1;
  • temp is a keyword.
  • 1==1 is invalid.
  • 1==1 evaluates to a Boolean.
  • Nothing is wrong with it.

Q37. What is special about the code within this block?

dispatch_async(dispatch_get_main_queue(), ^{
// code
  • It executes on the main queue.
  • It is the last code to run before the app goes inactive.
  • It executes on a background thread.
  • It is queued to execute in the background.

Q38. How many items are in set1 after this code executes?

NSMutableSet *set1 = [NSMutableSet setWithObjects: @1,@2, @3, @4, @5, nil];
[set1 add0bject:@3];
  • zero
  • six
  • one
  • five

Q39. What is wrong with this code?

NSDictionary *d1 = @[@"v1", @4, @"v2", @5.6, @"v3"];
NSlog(@"d1: %@", d1);
  • NSDictionary cannot be printed this way.
  • The last key is missing a value.
  • Dictionaries cannot have mixed types as values.
  • d1 is assigned an NSArray of values.

Q40. What is the initial value of the property val?

@property (nonatomic, readonly) int val;
  • 8
  • nil
  • -1
  • undefined

Hope you find this helpful!

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Darsh Jariwala
Darsh Jariwala

A web geek, game lover residing in India 🇮🇳