Craig's Answer

[howcr]

Hi,

Interface:

Code: (Objective-C)

#import <Cocoa/Cocoa.h>

@interface Rectangle : NSObject 
{
	int width; 
	int height;
}

-(void) setWidth: (int) w; 
-(void) setHeight: (int) h; 
-(int) width; 
-(int) height; 
-(int) area;
-(int) perimeter; 

@end

Implementation:

Code: (Objective-C)

#import "Rectangle.h"

@implementation Rectangle

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

-(void) setHeight: (int) h
{
	height = h;
}

-(int) width
{
	return width;
}

-(int) height
{
	return height;
}

-(int) area
{
	// A = H * W		
	return height * width;
}

-(int) perimeter
{
	// P = 2(H) + 2(W)
	int x = 2;
	return (x * height) + (x * width);
}

@end

Test Program:

Code: (Objective-C)

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

int main (int argc, const char * argv[]) {
    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];

    //CH - create an instance of a Rectangle
   Rectangle *myRect = [[Rectangle alloc]init];
	
    //CH - set the rectangle height & width 
    [myRect setHeight: 3];
    [myRect setWidth: 4];
	
    //CH - print out the results
    NSLog(@"Height: %i",[myRect height]);
    NSLog(@"Width: %i",[myRect width]);
    NSLog(@"Area: %i",[myRect area]);
    NSLog(@"Perimeter: %i",[myRect perimeter]);
	
    [myRect release];
	
    [pool drain];
    return 0;
}

Output:

Code: (Objective-C)

[Session started at 2009-09-08 14:13:10 -0400.]
2009-09-08 14:13:10.899 ch4_question7[45380:10b] Height: 3
2009-09-08 14:13:10.907 ch4_question7[45380:10b] Width: 4
2009-09-08 14:13:10.916 ch4_question7[45380:10b] Area: 12
2009-09-08 14:13:10.927 ch4_question7[45380:10b] Perimeter: 14

The Debugger has exited with status 0.

Regards,
Craig

[skochan]

Good job, Craig.   Now rewrite it to use the @property directive, synthesize your accessor methods, and use the dot operator.

Cheers,

Steve Kochan