Exercise 8-6 Kochan 2.0

[mdeh]

Write a Rectangle method called intersect: that takes a rectangle as an argument and returns a rectangle representing the overlapping area between the two rectangles. So, for example, given the two rectangles shown in Figure 8.9, the method should return a rectangle whose origin is at (400, 380), whose width is 50, and whose height is 60.



Rectangle.h


#import <Foundation/Foundation.h>
#import "XYPoint.h"

@interface Rectangle : NSObject {
int height;
int width;
XYPoint *origin;
}
@property int height, width;

/* setters */

-(XYPoint *) origin;

-(void) SetOrigin: (XYPoint *) pt;

-(void) setWidth: (int) w andHeight: ( int) h;

/* utility */

-(void) dealloc;

-(int) area;
-(int) perimeter;

-(Rectangle *) intersect: (Rectangle *) myRect;

-(BOOL) rectangleIntersectsWith: (Rectangle *) theRect;

@end


rectangle.m

#import "Rectangle.h"



@implementation Rectangle

@synthesize width, height;


-(void) SetOrigin: (XYPoint *) pt
{
if (origin)
[origin release];

origin = [[ XYPoint alloc] init] ;
[origin setX: pt.x andY: pt.y];
}


-(XYPoint *) origin
{
return origin;
}


-(int) area
{
return width * height;
}

-(int) perimeter
{
return 2 * ( width + height );
}

-(void) setWidth: (int) w andHeight: ( int) h
{
width = w;
height = h;
}

-(Rectangle *) intersect: (Rectangle *) myRect
{
BOOL overLap;
BOOL argumentISLower = NO;

Rectangle *returnRect = [[Rectangle alloc] init];
XYPoint *retPt = [ [ XYPoint alloc ] init];


overLap = [self rectangleIntersectsWith: myRect];
argumentISLower = origin. y > myRect.origin.y;



if (overLap == NO)
{
returnRect.origin.x = 0;
returnRect.origin.y = 0;
returnRect.width = 0;
returnRect.height = 0;
}

else

{

retPt.x = (myRect.origin.x > origin.x ) ? myRect.origin.x : origin.x;
retPt.y = origin.y;
[returnRect SetOrigin: retPt];
returnRect.height = (argumentISLower == YES) ? myRect.origin.y + myRect.height - origin.y : origin.y \
+ height - myRect.origin.y;
returnRect.width = (myRect.origin.x > origin.x) ? origin.x + width - myRect.origin.x : myRect.origin.x \
+ myRect.width - origin.x;
}

[retPt release];

return returnRect;
}

-(BOOL) rectangleIntersectsWith: (Rectangle *) theRect
{


/* one rectangle is above or below the other */
if ( origin.y > theRect.origin.y + theRect.height || origin.y + height < theRect.origin.y)
return NO;

/* one rectangle is either to the left or right */
if ( origin.x + width < theRect.origin.x || theRect.origin.x + width < origin.x)
return NO;

return YES; /* all other conditions should overlap */
}


-(void) dealloc
{

[origin release];
[super dealloc];
}



@end



XYPoint.h


#import <Foundation/Foundation.h>


@interface XYPoint : NSObject {
int x;
int y;
}

@property int x, y;

-(void) setX: (int) xVal andY: (int) yVal;

@end



XYPoint.m


#import "XYPoint.h"


@implementation XYPoint

@synthesize x, y;

-(void) setX: (int) xVal andY: (int) yVal
{
x = xVal;
y = yVal;
}


@end



main.h


#import "Rectangle.h"
#import "XYPoint.h"

int main (int argc, const char * argv[]) {
NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
Rectangle *resRectangle;
Rectangle * rect1 = [[ Rectangle alloc] init];
Rectangle * rect2 = [ [ Rectangle alloc] init];
XYPoint *myPt1 = [ [ XYPoint alloc] init];
XYPoint *myPt2 = [ [ XYPoint alloc] init];

myPt1.x = 200;
rect1.height = 75;
rect1.width = 250;


rect2.width = 100;
rect2.height = 180;
myPt2.x = 150;
myPt2.y = 300;
[rect2 SetOrigin: myPt2 ];

for (myPt1.y = 200; myPt1.y <= 500; myPt1.y ++){
[rect1 SetOrigin: myPt1];
resRectangle = [rect1 intersect: rect2 ];
NSLog(@" New rectangle: {Pt(%3i,%3i)} Width(%-2i), Height(%-3i), Origin(%3i,%3i)", myPt1.x, myPt1.y, resRectangle.width, resRectangle.height,\
resRectangle.origin.x, resRectangle.origin.y);
[resRectangle release];
}

[rect1 release];
[rect2 release];
[myPt1 release];
[myPt2 release];


[pool drain];
return 0;
}




Look forward to anyone's input.

[TotalLuck]

Hey Mdeh,
you went way deeper than i did and now i need to relook at my code. thanks for posting that. I'm posting what i wrote just for kicks and mockery.

Rectangle.m

-(Rectangle *) intersect: (Rectangle *) bRect
{
Rectangle *overlapRect = [[ Rectangle alloc] init];
XYpoint *overlapPT = [[ XYpoint alloc] init];

overlapRect.height = self.origin.y - bRect.origin.y - bRect.height;
if (overlapRect.height <= 0)
overlapRect.height *= -1;

overlapRect.width = self.width - bRect.origin.y;
if (overlapRect.width <= 0)
overlapRect.width *= -1;

[overlapPT setX: bRect.origin.x andY:self.origin.y];
[overlapRect setOrigin: overlapPT];

NSLog(@"The Intersect Rectangle is %gw x %gh with origin at %g,%g", overlapRect.width, overlapRect.height, overlapPT.x, overlapPT.y);

[overlapPT release];
[overlapRect release];
return 0;
}


rectangle.h

@interface Rectangle : GraphicObject
{
double width;
double height;
XYpoint *origin;
}

@property double width, height;

-(XYpoint *) origin;
-(void) setOrigin: (XYpoint *) pt;
-(double) area;
-(double) perimiter;
-(void) setwidth: (double) w andheight: (double) h;
-(XYpoint *) translate: (XYpoint *) mypt;
-(void) draw;
-(Rectangle *) intersect: (Rectangle *) bRect;
@end


Main.m
int main(int argc, char *argv[])
{
NSAutoreleasePool * pool = [[NSAutoreleasePool alloc]init];
Rectangle *rectA = [[ Rectangle alloc] init];
Rectangle *rectB = [[ Rectangle alloc] init];
XYpoint *rectAPT = [[ XYpoint alloc] init];
XYpoint *rectBPT = [[ XYpoint alloc] init];


[rectAPT setX:200 andY: 420];
[rectA setwidth:250 andheight:75];
[rectA setOrigin: rectAPT];

NSLog(@"Rectangle A is %gw x %gh with origin at %g,%g", rectA.width, rectA.height, rectA.origin.x, rectA.origin.y);

[rectBPT setX:400 andY:300];
[rectB setwidth:100 andheight:180 ];
[rectB setOrigin: rectBPT];

NSLog(@"Rectangle B is %gw x %gh with origin at %g,%g", rectB.width, rectB.height, rectB.origin.x, rectB.origin.y);

[rectA intersect: rectB];

[rectB release];
[rectA release];
[rectBPT release];
[rectAPT release];


return 0;
[pool release];

}

my result:
Rectangle A is 250w x 75h with origin at 200,420
Rectangle B is 100w x 180h with origin at 400,300
The Intersect Rectangle is 50w x 60h with origin at 400,420


***ok I didnt red the part at the bottom where it said to return a 0,0 for origin and 0 for w and h if they dont intersect. DUH