Question

I have two classes: Geometry and Circle. Circle is a subclass of Geometry.

Geometry has a synthesized property:

interface:

@interface Geometry : NSObject <drawProtocol, intersectionProtocol>
@property int geoLineWidth;

implementation:

@synthesize geoLineWidth;

Circle is a subclass of Geometry. The interface:

@interface Circle : Geometry

This code compiles, inside a method of Geometry, in Geometry.m

NSLog(@"%d", geoLineWidth);

This code does not compile, inside a method of Circle

NSBezierPath * thePath=  [NSBezierPath bezierPath];
[thePath setLineWidth: geoLineWidth];

Use of undeclared identifier 'geoLineWidth'

However, this code compiles:

[thePath setLineWidth: [self geoLineWidth]];

Is this behavior intentional, or am I missing something ?

Answer 1

In the subclass, instead of accessing the instance variable directly, you must actually use the accessor.

Change this:

[thePath setLineWidth: GeoLineWidth];

To this:

[thePath setLineWidth: self.GeoLineWidth];
[thePath setLineWidth: [self GeoLineWidth]];

To get the compiler to recognize the instance variable, you’d need explicitly to declare it in the superclass header file.