Is there something wrong with my object?

This is a program that I am writing (I am not against copying someone else and therefore not learning) as part of the ObjectiveC and Cocoa learning curve. I want to draw simple shapes in NSView (limiting it to ovals and rectangles for now). The idea is that I write every NSBezierPath to an NSMutableArray, so I can also investigate / implement save / load, undo / redo. I have a canvas that I can draw on and also 2 buttons that I use to select a tool. To handle the path, I created another object that can contain an NSBezierPath, color values, and a size value for each object drawn. This is what I want to store in the array. I am using mouseDown / Dragged / Up to get the coordinates for the drawing path. However, this is where things get uncomfortable. I can instantiate an object,which should contain the path / color / etc. info, but when I try to change the instance variable, the application crashes without a helpful message in the debugger. I'll try to keep my code snippets short, but tell me if you need to include more. The code has also degenerated a bit from me, trying to do so many things to make it work.

Project: Cocoa document based application
I have the following .m / .h files

•  
• MyDocument:NSDocument
  
  - generated by Xcode 
• DrawnObject:NSObject
  
  - handles the drawn object, i.e. path, color, type (oval / straight) and size 
• Canvas:NSView
  
  - well, shows a picture, deals with mouse and buttons

Canvas is also responsible for persisting NSMutableArray

objects DrawnObject

.

DrawnObject.h

as follows:

#import <Foundation / Foundation.h>
// The drawn object must know what tool it was created with etc as this needs to be used for generating the drawing

@interface DrawnObject: NSObject {
    NSBezierPath * aPath;
    NSNumber * toolType; // 0 for oval, 1 for rectangular etc ....
    float toolSize;
    struct myCol {
        float rd;
        float grn;
        float blu;
        float alp;
    } toolColor;
}

- (void) setAPath: (NSBezierPath *) path;
- (NSBezierPath *) aPath;
@property (readwrite, assign) NSNumber * toolType;
- (float) toolSize;
- (void) setToolSize: (float) size;
- (struct myCol *) toolColor;
- (void) setCurrentColor: (float) ref: (float) green: (float) blue: (float) alpha;

@end

Canvas.h

as follows

#import 
#import "drawnObject.h"

@interface Canvas: NSView {
    NSMutableArray * myDrawing;
    NSPoint downPoint;
    NSPoint currentPoint;
    NSBezierPath * viewPath; // to show the path as the user drags the mouse
    NSNumber * currentToolType;
    BOOL mouseUpFlag; // trying a diff way to make it work
    BOOL mouseDrag;
}

- (IBAction) useOval: (id) sender;
- (IBAction) useRect: (id) sender;
- (IBAction) showTool: (id) sender;
- (NSRect) currentRect;
- (NSBezierPath *) createPath: (NSRect) aRect;
- (void) setCurrentToolType: (NSNumber *) t;
- (NSNumber *) currentToolType;
@end

There Canvas.m

are several functions in the file for working with the mouse, and NSView / XCode also crashed in
-(id)initWithFrame:(NSRect)frame

and -(void)drawRect:(NSRect)rect

I originally use mouseUp

to try to insert a new one DrawnObject

into the array but this crashed. So now I'm using two flags BOOL

to see when the mouse was released (clumsy, but I'm trying ...) in drawRect

order to insert into the array. I've included the method below and pointed out where it is causing the application to crash:

- (void) drawRect: (NSRect) rect {// This is called automatically
    // Drawing code here.
    // NSLog (@ "Within drawRect tool type is% d", [self currentTool]);
    NSRect bounds = [self bounds];
    NSRect aRect = [self currentRect];
    viewPath = [self createPath: aRect];
// the createPath method uses the tool type to switch between oval and rect bezier curves

    if (mouseUpFlag == YES && mouseDrag == YES) {
        mouseDrag = NO;
        // Create a new drawnObject here 
        DrawnObject * anObject = [[DrawnObject alloc] init]; // - WORKS FINE UP TO HERE
        NSLog (@ "CREATED NEW drawnObject");
        [anObject setAPath: viewPath]; // - INSTANT APP DEATH !!!!
        NSLog (@ "Set a path in drawnObject");
        [anObject setToolType: [[NSNumber alloc] initWithInt: 5]];
        NSLog (@ "Set toolType in DrawnObject");
        [anObject setToolType: currentToolType];

        [myDrawing addObject: anObject];
        NSLog (@ "Added Object");
    }   

    [[NSColor colorWithCalibratedRed: 0.0 green: 0.9 blue: 0.0 alpha: 0.5] set];
    [NSBezierPath fillRect: bounds];


    [[NSColor lightGrayColor] set];
    [viewPath stroke]; // This is so the user can see where the drawing is being done

    // Now, draw the paths in the array
    [[NSColor blueColor] set];
    for (DrawnObject * indexedObject in myDrawing) {
        [[indexedObject aPath] stroke]; // This will do the actual drawing of ALL objects

    }


}

I'm guessing it has something to do with the object realm or something, but I just can't figure it out. As I said, since I've tried things, the code seems to have undergone a metamorphosis, unfortunately not for the best. Like those BOOLS etc.

HELP! Any smart people out there, point me in the right direction please!

ADD THIS ON:

-(NSBezierPath *)createPath:(NSRect) aRect
{

    NSBezierPath * tempPath;
    //I need to know what tool

    switch(0){  //temporary - this would use the toolType as a selector
        case 0:
            tempPath = [NSBezierPath bezierPathWithOvalInRect:aRect];
            break;
        case 1:
            tempPath = [NSBezierPath bezierPathWithRect:aRect];
            break;
        default:
            tempPath = [NSBezierPath bezierPathWithOvalInRect:aRect];
            break;
    }
    return tempPath;
}