Question

I am following along with a series of web tutorials relating to Objective-C and am now getting a “Accessing unknown origin getter method” error when i try to build my program (origin being a member of a Rectangle class that I created).

Here is my class titled PointXY:

#import <Foundation/Foundation.h>      
@interface PointXY : NSObject 
{
    int x;
    int y;
}

//Setters and Getters
@property int x;
@property int y;

//Methods
- (void) setXY : (int) xCO : (int) yCO;

@end

I then define a rectangle class, that has a member that is of type PointXY:

#import <Foundation/Foundation.h>
@class PointXY;
@interface rectangle : NSObject 
{
    float width;
    float height;
    PointXY * origin;

}

//Setters and Getters
@property float width, height;

//Instance Methods
- (float) getArea;
- (float) getPerimeter;

//We already have setters and getters defined for width
//and height. The below method is for illustration purposes
- (void) setHW: (float) h : (float) w;

//Methods to set and get origin values
- (PointXY *) getOrigin; //Returns a PointXY object
- (void) setOrigin : (PointXY *) point;

@end

I get the error in main, if i try to access the x or y property of my origin member via my NSLog statement:

#import <Foundation/Foundation.h>
#import "rectangle.h"
#import "PointXY.h"

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

    //Create an object
    rectangle * myRectangle = [[rectangle alloc]init];
    PointXY * rOrigin = [[PointXY alloc]init];

    [rOrigin setXY:100 :100];
    myRectangle.origin = rOrigin;


    NSLog(@"The origin for the rectangle is %i, %i", myRectangle.origin.x, myRectangle.origin.y);


    [pool drain];
    return 0;
}

I understand that one cannot access the members without either explicitly defining a synthesized accessor or by creating a method to do just that and was surprised to see the author of the tutorial do the above with no issue.

Is the above even possible? Can I access myRectangle.origin.x without origin being synthesized in myRectangle or do I have something set up incorrectly.

Thanks for your time.

Answer 1

Origin is an instance variable you need to create an @property for it and synthesize it as you already know.

//Setters and Getters
@property float width, height;
@property PointXY *origin;

But without the property you could access the origin by doing this rectangle->origin but that defeats the purpose of encapsulation.

Edit- origin will need to be defined as @public or @package