There is an explanation of why OOPs and then there is detailing on how OOPs is used by Objective C.

1. Tiyasi Acharya

2. Why OOPs?
• Spaghetti code.
• Mass of tangled jumps and conditional
branches.
• Not designed for efficiency.

3. Performance
Time/Size
Complexity

4. Performance
OOPs
Time/Size
Complexity

5. How did OOPs come into the picture?
Abstraction
‘Emulate the working of a brain’ ‘Abstract out the details’

7. Internal Model of a Car

8. Internal Model of a Car
This is what computer scientists tried to bring into OOPs- ABSTRACTION!

9. Abstraction

10. Abstraction
This is how the human brain handles the complexity of the world.

11. Abstraction
This is how the human brain handles the complexity of the world.
How is this achieved in OOPs?

12. Inheritance
Process by which 1 object acquires the properties of another object.
Super Class: Four-wheeler Vehicles
Sub Class: Truck, Car, Bus.

13. Encapsulation
“Hides” incredible amount of complexity by encapsulating it.

14. Encapsulation
What was it hiding?

15. Polymorphism
A feature that allows 1 interface to be used for a general class of actions.
Steering Wheel
Power Steering Wheel Steering wheel of an Electric car

16. Another example of Polymorphism
Dog Smell

17. Class and Objects

18. OOPs in Objective C

19. Class and Objects
A class consists of members: data and methods.
Class Name
@interface Employee: NSObject
{
int empId;
char *name; Members: Data
}
-(int) empId;
Members: Methods
-(int)lengthOfService:date;
@end

20. Objects
id date=[ [ Date alloc ] init ]; New Date object allocated
[ date release];
Releasing the variable

21. Inheritance
Superclass Rectangle.m
#import “Rectangle.h”
Superclass Rectangle.h
@implementation Rectangle
@interface Rectangle: NSObject
{ -(id) init
int length; {
int width; if(self=[super init])
} {
length = 8;
-(int) area; width = 5;
}
@end return self;
}
-(int) area
{
int area1=length * width;
}
@end

22. Inheritance
Subclass printAreaOfRectangle.h
#import “Rectangle.h”
@interface printAreaOfRectangle: Rectangle
-(void) printVal;
@end
Subclass printAreaOfRectangle.m
#import “printAreaOfRectangle.h”
@implementation printAreaOfRectangle
(void) printVal
{
NSLog(@”Area = %d”,[self area]);
}
@end

23. Encapsulation
• All the data members are ‘Protected’.
• Data is encapsulated, can be accessed only through
setter/getter methods.

24. Polymorphism
main
{
Window *W = [[Window alloc] init];
View *V = [[view alloc] init];
[W flush];
[V flush];
}

25. Dynamic binding + Message Passing
main
{
Window *W = [[Window alloc] init];
View *V = [[view alloc] init];
[W flush];
[V flush];
id anotherObj = W; Dynamic Binding
[anotherObj flush]; Message Passing
}
The flush message is passed to the variable anotherObj that is dynamically bound during runtime.

26. Summary
The OOPs features that Objective C exhibits are as follows:
• Abstraction
• Encapsulation
• Class
• Object
• Inheritance
• Polymorphism
• Message passing
• Dynamic Binding

27. Thank you