macOS Probably a Simple Problem...

[CaptainZap]

Well I am working my way through "Programming in Objective-C" book, and am currently stuck on an exercise in Chapter 8, unfortunately it is an even so I can't see what Kochan has on his site. So the question is,

4. Write a Rectangle method called translate: that takes a vector Point (xv,yv) as its argument. Have it translate the rectangle's origin by the specified vector.

So in the Rectangle.h, I made the method declaration,

-(Point *) translate: (Point *) vector;

and it is supposed to take a Point instance and translate it by its x and y values.

So I came up with this method definition...

-(Point *) translate: (Point *) vector;
{	
	float vectorX, vectorY;
		
	origin = [[Point alloc] init];
	
	vectorX = [[vector origin] x] + x;
	vectorY = [[vector origin] y] + y;
	
	[origin setX: vectorX setY: vectorY];
}

then in the main.m, I did this

int main (int argc, char *argv[])
{	
	Rectangle *myRectangle = [[Rectangle alloc] init];
	Point *myPoint = [[Point alloc] init];
	Point *translation = [[Point alloc] init];
	
	[myRectangle setHeight: 12];
	[myRectangle setWidth: 3];
	
	[myPoint setX: 6 setY: 7];

	[translation setX: 4 setY: 3];

	[myRectangle setOrigin: myPoint];
	
	[myRectangle translate: translation];

	printf ("Now the Origin is at (%g,%g)\n", [[myRectangle origin] x], [[myRectangle origin] y]);

	return 0;
}

I get the errors, error: 'x' undeclared (first use in this function) and the same for y, if you need the rest of the .m and .h files, just ask.

 

[bronxbomber92]

It would help to know what the structs/classes of Point and Rect contained

 

[CaptainZap]

K, for Rectangle...

@interface Rectangle: Object
{
	float height;
	float width;
	Point *origin;
}

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

-(void) setOrigin: (Point *) pt;
-(Point *) origin;

-(Point *) translate: (Point *) vector;

-(id) free;

@end

And for Point

@interface Point: Object
{
	float x;
	float y;
}

-(void) setX: (float) xVal;
-(void) setY: (float) yVal;
-(void) setX: (float) xVal setY: (float) yVal;

-(float) x;
-(float) y;

@end

P.S. I left out the preprocessor lines, so don't think that I forgot to put them in my program

 

[yoavcs]

You aren't defining the 'x' and 'y' local variables you use in the translate: method anywhere...

Edit for clarity: not the ones in the [[vector origin] x] message, the ones outside.

 

[CaptainZap]

You aren't defining the 'x' and 'y' local variables you use in the translate: method anywhere...

Edit for clarity: not the ones in the [ ] method call, the ones outside.

Ah, ok, I dunno why, but for some reason I kept thinking Rectangle inherited the methods from Point.

Woot, thanks, I got it, and if anyone is curious, I just changed the translate method so it doesn't return anything and to this

-(void) translate: (Point *) vector;
{	
	float vectorX, vectorY;
		
	Point* transOrigin = [[Point alloc] init];
	
	vectorX = [vector x] + [[self origin] x];
	vectorY = [vector y] + [[self origin] y];
	
	[transOrigin setX: vectorX setY: vectorY];
	
	[self setOrigin: transOrigin];
	
}