Calculation/variable returning as zero - objective-c

Question

I am setting up a basic geometry class where I define a rectangle and can manipulate the width and height along with calculating the area and perimeter. Everything works and outputs fine, except the perimeter and area variables return as zero. I don't know how to set the variable properly within itself or during the #implementation, so I'm sure it is showing the zero from when the variable is first initialized (before the width and height are set).
I'm inexperienced with OOP and ObjC so I may be missing something simple.
#import <Foundation/Foundation.h>
// #interface setup as required.
#interface Rectangle: NSObject
-(void) setWidth: (int) w;
-(void) setHeight: (int) h;
-(int) width;
-(int) height;
-(int) area;
-(int) perimeter;
-(void) print;
#end
// #implementation setup for the exercise.
#implementation Rectangle {
int width;
int height;
int perimeter;
int area;
}
// Set the width.
-(void) setWidth: (int) w {
width = w;
}
// Set the height.
-(void) setHeight: (int) h {
height = h;
}
// Calculate the perimeter.
-(int) perimeter {
return (width + height) * 2;
}
// Calculate the area.
-(int) area {
return (width * height);
}
-(void) print {
NSLog(#"The width is now: %i.", width);
NSLog(#"The height is now: %i.", height);
NSLog(#"The perimeter is now: %i.", perimeter);
NSLog(#"The area is now: %i.", area);
}
#end
int main(int argc, const char * argv[])
{
#autoreleasepool {
// Create an instance of Rectangle.
Rectangle *theRectangle;
theRectangle = [Rectangle alloc];
theRectangle = [theRectangle init];
// Use the designed methods.
[theRectangle setWidth: 100];
[theRectangle setHeight: 50];
[theRectangle print];
}
return 0;
}

Answer 1

Short answer:
Call your object methods like this:
[self perimeter];
// as in
NSLog(#"The perimeter is now: %i.", [self perimeter]);
instead of just
perimeter
which accesses the variable with that name, instead of calling the method you've defined.
Longer answer:
There are several things in your code that can be improved:
You should use properties instead of ivars and methods to get and set them. A property declared like this: #property (nonatomic) int width; will give you a getter and a setter, created implicitly by the compiler. So then you can do either of these to set a value:
theRectangle.width = 100;
// is the same as:
[theRectangle setWidth:100];
You can override your getters and setters too. You could also create readonly properties, e.g.
#interface Rectangle: NSObject
#property (nonatomic) int width;
#property (nonatomic) int height;
#property (nonatomic, readonly) int perimeter;
#end
#implementation Rectangle
- (int)perimeter
{
return self.width * self.height * 2;
}
#end