polymorphism methods in ios - objective-c

Question

I have a doubt in implementing oops concept in objective-c.Is Pholyorphism possible in objective-c. How to implement polymorphism in objective-c.please explain with example?

Answer 1

Every method, including class methods, is dynamic in Objective-C.
One very basic approach would be:
Declare the base interface:
#interface MONConstantColor : NSObject
- (UIColor *)color;
#end
Define the base implementation:
#implementation MONConstantColor
- (UIColor *)color { return /* ...do/ret something appropriate */; }
#end
Then create some variations:
#interface MONRedColor : MONConstantColor
#end
#implementation MONRedColor
- (UIColor *)color { return [UIColor redColor]; }
#end
#interface MONYellowColor : MONConstantColor
#end
#implementation MONYellowColor
- (UIColor *)color { return [UIColor yellowColor]; }
#end

Answer 2

- (HomeWorkResult *)homeWorkResultFromHomeWorkTask:(HomeWorkTask *)task
{
if (!self.lazy) {
return [self HW_performHomeWorkTask:task];
}
StackOverflowPost *post = [StackOverflow postHomeWorkTask:task];
for (id user in post.responders) {
// Here is the pholyorphism[sic].
// First, test to see if a stack overflow user is able to do home work tasks.
if ([user respondsToSelector:#selector(homeWorkResultFromHomeWorkTask:)]) {
// Next, have the user do the home work task.
HomeWorkResult *result = [user homeWorkResultFromHomeWorkTask:task];
// If there is a result, return that result.
if (result) {
return result;
}
}
}
// Finally, if no stack overflow user does home work tasks or if there was no
// result perform the task yourself.
return [self HW_performHomeWorkTask:task];
}

Answer 3

The word polymorphism means having many forms
Objective-C polymorphism means that a call to a member function will cause a different function to be executed depending on the type of object that invokes the function.
Consider the example, we have a class Shape that provides the basic interface for all the shapes. Square and Rectangle are derived from the base class Shape.
We have the method printArea that is going to show about the OOP feature polymorphism.
#import <Foundation/Foundation.h>
#interface Shape : NSObject
{
CGFloat area;
}
- (void)printArea;
- (void)calculateArea;
#end
#implementation Shape
- (void)printArea{
NSLog(#"The area is %f", area);
}
- (void)calculateArea{
}
#end
#interface Square : Shape
{
CGFloat length;
}
- (id)initWithSide:(CGFloat)side;
- (void)calculateArea;
#end
#implementation Square
- (id)initWithSide:(CGFloat)side{
length = side;
return self;
}
- (void)calculateArea{
area = length * length;
}
- (void)printArea{
NSLog(#"The area of square is %f", area);
}
#end
#interface Rectangle : Shape
{
CGFloat length;
CGFloat breadth;
}
- (id)initWithLength:(CGFloat)rLength andBreadth:(CGFloat)rBreadth;
#end
#implementation Rectangle
- (id)initWithLength:(CGFloat)rLength andBreadth:(CGFloat)rBreadth{
length = rLength;
breadth = rBreadth;
return self;
}
- (void)calculateArea{
area = length * breadth;
}
#end
int main(int argc, const char * argv[])
{
NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
Shape *square = [[Square alloc]initWithSide:10.0];
[square calculateArea];
[square printArea];
Shape *rect = [[Rectangle alloc]
initWithLength:10.0 andBreadth:5.0];
[rect calculateArea];
[rect printArea];
[pool drain];
return 0;
}
use this link as refernce
http://www.tutorialspoint.com/objective_c/objective_c_polymorphism.htm