How to display unarchived custom NSView objects

Question

I’m learning Cocoa programming, and I’m unable to figure out how to archive and unarchive a custom NSView subclass

I’ve made a toy application that presents a window. This window contains an instance of my custom BackgroundView class (archived in the xib file). Clicking anywhere in this BackgroundView creates and displays a blue square whose origin is the click point. This square is an instance of my Square class. All of this works as I expect.

The Square class implements the NSCoding protocol. I’ve added dataOfType: typeName: error: and readfromData: ofType: error: methods to the MyDocument class. As far as I can tell from log statements, the Squares are being archived to the file, and unarchived when the file is loaded. But I’m unable to make the squares display themselves on the window. The Square class’s drawWithRect: method is never called, even though I’ve called setNeedsDisplay:YES on each square.

The code is as follows:

Square.h
#import <Cocoa/Cocoa.h>
@interface Square : NSView <NSCoding> {
}
@end

Square.m
#import "Square.h"
@implementation Square

- (id)initWithFrame:(NSRect)frame {
   self = [super initWithFrame:frame];
   return self;
}

- (void)drawRect:(NSRect)rect {
       [[NSColor blueColor] set];
       NSBezierPath *newPath = [NSBezierPath bezierPathWithRect:[self bounds]];
       [newPath fill];
}

-(void)encodeWithCoder:(NSCoder *)coder
{
       [coder encodeRect:[self frame] forKey:@"frame"];
}

-(id)initWithCoder:(NSCoder *)coder
{
       NSRect theRect = [coder decodeRectForKey:@"frame"];
       self = [super initWithFrame:theRect];
       return self;
}
@end
-----
BackgroundView.h
#import <Cocoa/Cocoa.h>
@interface BackgroundView : NSView {
}
@end

BackgroundView.m
#import "BackgroundView.h"
#import "Square.h"
@implementation BackgroundView

- (id)initWithFrame:(NSRect)frame {
   self = [super initWithFrame:frame];
   if (self) {
       // Initialization code here.
   }
   return self;
}

- (void)drawRect:(NSRect)rect {
       for (Square *subview in self.subviews)
               [subview setNeedsDisplay:YES];
}

-(void)mouseDown:(NSEvent *)theEvent {
       NSPoint unsetClick = [theEvent locationInWindow];
       NSPoint theClick = [self convertPoint:unsetClick fromView:nil];
       NSRect theRect;
       theRect.origin = theClick;
       theRect.size.width = 100.00;
       theRect.size.height = 100.00;
       Square *newSquare = [[Square alloc] initWithFrame:theRect];
       [self addSubview:newSquare];
       [newSquare setNeedsDisplay:YES];
}
@end
------
MyDocument.h
#import <Cocoa/Cocoa.h>
@class BackgroundView;

@interface MyDocument : NSDocument
{
       IBOutlet BackgroundView *theBackgroundView;
}
@end

MyDocument.m
#import "MyDocument.h"

@implementation MyDocument

- (id)init
{
   self = [super init];
   return self;
}

- (NSString *)windowNibName
{
   return @"MyDocument";
}

- (void)windowControllerDidLoadNib:(NSWindowController *) aController
{
   [super windowControllerDidLoadNib:aController];
}

- (NSData *)dataOfType:(NSString *)typeName error:(NSError **)outError
{
   return [NSKeyedArchiver
archivedDataWithRootObject:[theBackgroundView subviews]];
   if ( outError != NULL ) {
               *outError = [NSError errorWithDomain:NSOSStatusErrorDomain
code:unimpErr userInfo:NULL];
       }
       return nil;
}

- (BOOL)readFromData:(NSData *)data ofType:(NSString *)typeName
error:(NSError **)outError
{
   [theBackgroundView setSubviews:[NSKeyedUnarchiver
unarchiveObjectWithData:data]];
   [theBackgroundView setNeedsDisplay:YES];
   if ( outError != NULL ) {
               *outError = [NSError errorWithDomain:NSOSStatusErrorDomain
code:unimpErr userInfo:NULL];
       }
   return YES;
}

@end

Answer 1

As I can see you don't add any of the initWithXXX and encodeWithXXX methods since you don't have custom member variables.

I suggest to check out Apple's Sketch Example.