Objective-C Test

What is the value of s?
NSMutableString *s = [NSMutableString stringWithString:@"123"];
 [s appendString:@"456"];

• 123
• 123456
• 456
• This code contains an error.
   

What's the value of i after these statements?
NSString *str = nil;
NSInteger i = str.integerValue;

• This code crashes.
• nil
• -1
• 0
   

What value is in str after this line is executed?
NSString str = "test" + " " + "more";

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

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);

• Nothing, since this code contains an error.
• 1,2
• 2
• 1,2,3
   

What is foo?
-(float)foo;

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

What can you glean from this line?
#import "NSString+NameHelper.h"

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

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 statement.
   

How many times with this loop be executed?
for (int x=0; x<100; x++) {
 x = x + 1;
}

• 50
• This code contains an error.
• 100
• 99
   

What is printed for this code?
int val = 0;
 val = 1.5;
 printf ("%d", val);

• 2
• This code contains an error.
• 1
• 0
   

How many keys does this NSDictionary have after this code is executed?
NSDictionary *dict = [[NSDictionary alloc] initWithObjectsAndKeys:
  @"b",@"e",@"a",@"r", nil];

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

What is wrong with this code?
NSMutableDictionary *dict1 = [NSMutableDictionary dictionaryWithCapacity:5];
[dict1 setValue:@"key" forKey:@"value"];

• The key and value items are mixed.
• You can't set the capacity on a dictionary.
• NSMutableDictionary doesn't have a :setValue:forKey function.
• Nothing is wrong with it.
   

What is printed from this code?
NSData *data = [@"print" dataUsingEncoding:NSASCIIStringEncoding];
NSLog(@"%@", [[NSString alloc] initWithData:data encoding:NSASCIIStringEncoding]);

• <nil>
• This code is invalid.
• print
• Nothing is printed from this code.
   

What is different about this function?
+(void)doSomething;

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

What's wrong with this code?
@interface MyClass : NSObject
        @property (strong,nonatomic, readonly) NSString *name;
    @end

• There is no read-only directive.
• MyClass doesn't implement NSObject.
• Properties are declared in the implementation.
• There is nothing wrong with this code.
   

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"
• This code contains an error.
• nil
• 2,3
   

What is an enums base type for the code below?
typedef enum { Foo1, Foo2 } Foo;

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

What is this Objective-C code checking?
if ([keyPath isInstanceOf:[NSString class]]) {
}

• if keyPath is an instance of NSString
• This code contains an error.
• if keyPath's baseclass is the same as NSString's baseclass
• if keyPath implements the same methods as NSString
   

For observing changes to a property, which of these two statements causes the related method to be called and why?
1. _val = 1;
2. self.val= 100;

• Statement 1, since it uses the property directly.
• Statement 2, since it calls the auto-created setter on the property.
• Statement 1, since it calls the auto-created setter on the property.
• Statement 2, since it specifies the class instance to use.
   

What's wrong with this code?
float x = 2.0;
int (^foo)(int) = ^(int n1){
 return (int)(n1*x);
};
foo(5);

• x is not in the right scope.
• Nothing is wrong with this code.
• Ints and floats can't be multiplied.
• The parameter isn't declared correctly.
   

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];
   

What is this a declaration of?
int(^foo)(int);

• a block of code
• a Generic
• an abstract class
• an Extension
   

What's 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.