Objective C

Question 1

Why can C programs be ran in O-C?

Answer 1

Objective C is a superset of C.

Question 2

Similarities between Objective-C and C++

and differences

Answer 2

Object Orientation

Objective C has no function or operator overloading.

Question 3

Objective-C:

Answer 3

C plus objects
A strict superset of C
C++ vs Objective-C:
C++ : a better C
O-C: a better way of soldering components together

Question 4

Objective C frameworks:

Answer 4

2 OOP frameworks
Foundation: classes for basic data structures and interacting with OS
AppKit: classes for developing applications, windows, buttons, etc

Question 5

Objective-C 2.0 adds

Answer 5

garbage collection <<< !!!
syntax enhancements
runtime performance improvements
64 bit support
features such as properties and fast enumerators

Question 6

Objective C class declaration

Answer 6

@interface SampleClass:NSObject
- (void) sampleMethod;
@end

Question 7

Objective C class implementation

Answer 7

@implementation SampleClass
-(void) sampleMethod()
@end

Question 8

What is #import

Answer 8

Bit like #include

Question 9

Hello world

Answer 9

#import 
int main()
{
     NSLog(@"Hello world!\n");
     printf("%s\n", [@"Hello world!\n" UTF8String]);
     return 0;
}
printf understands UTF8.

Question 10

Objective C code unit extension

Answer 10

.m

Question 11

Wrapper classes

Answer 11

NSNumber
int float double boolean
NSString and NSMutableString
unicode strings (usually UTF-16)
NSArray and NSMutableArray
dynamic arrays

Question 12

Objects must always be:

Answer 12

pointers
i.e. NSNumber *num
Memory for objects is always allocated on the heap

Question 13

Creating objects

Answer 13

NSNumber *num1
NSNumber *num2 = [NSNumber alloc]
NSNumber *num3a = [[NSNumber alloc] init]
NSNumber *num3b = [NSNumber new]
NSNumber *num4 = [[NSNumber alloc] initWithInteger:43]
^^^ num4 correct

Question 14

What do all classes inherit from?

Answer 14

NSObject

Question 15

Method declaration

Answer 15

-(void)setFirstName: (NSString *) name;

Question 16

• vs +

Answer 16

- instance method
\+ class method (static)

Question 17

Memory allocation

Answer 17

C malloc, free (from heap)
C++ new, delete
O-C, constructors name begins with init, called after alloc i.e. [[NSNumber alloc] initWithInteger:@43];

Question 18

What is id

Answer 18

Datatype that is a pointer to any type of object
Supports dynamic referencing, object type defined at runtime.
(id) init
(Money *) init