macOS More Drag & drop, drawRect question

[mdeh]

I have written a little app to **finally** try and answer a Hillegass challenge, which tries to further my understanding of Drag & Drop.

So, I have a subclassed NSView, which has the following methods implemented.

To register:

-(void) awakeFromNib
{
	
	NSArray *pbTypes = [ NSArray arrayWithObjects:NSPasteboardTypeString, NSPasteboardTypeSound, NSColorPboardType, nil];
	 [self registerForDraggedTypes : pbTypes];
	
	NSLog(@"Registered for drop: \"String\", \"Sound\", \"Color\"");
}

On entering ( with the drag)

- (NSDragOperation)draggingEntered: (id < NSDraggingInfo >)sender
{
	
	NSDragOperation sourceDragMask;
	NSPasteboard *pboard;
	
	pboard = [ sender draggingPasteboard];
	sourceDragMask = [ sender draggingSourceOperationMask];
	
	if ( [[ pboard types] containsObject: NSColorPboardType])
	{
		if ( sourceDragMask & NSDragOperationGeneric)
		{
			NSLog(@"Will respond to color");
			return NSDragOperationGeneric;
			
			
		}
	}
	
	....code to check for StringType......
	
	return NSDragOperationNone;
	
}

And on the "drop"

- (BOOL)performDragOperation: (id <NSDraggingInfo>)sender
{
	NSPasteboard *pboard;
	NSDragOperation sourceDragMask;
	
	sourceDragMask = [ sender draggingSourceOperationMask];
	pboard = [ sender draggingPasteboard];
	
	if ( [[ pboard types]  containsObject:NSColorPboardType] )
	{
		NSColor *newColor = [ NSColor colorFromPasteboard:pboard];
		[newColor set];
		[self setNeedsDisplay:YES];
....other code....

return YES;

Now, here is the problem:

in drawRect: I set the current graphics context to the fill/stroke color. However, in order to use the "dragged" color, I clearly have to somehow take the "newColor" from the "performDragOperation" and use *that* in drawRect. Initially, I tried to see if there is a way I can interrogate the current Context from drawRect, and in that way, I could set an initial value for NSColor, say from awakeFromNib, but I cannot find a way to do this. Then I thought of extracting the color directly from the draggingPasteBoard, but could not figure out a way of referencing that from drawRect. This is cocoa, so I **know** there is an easy way to do this.
It might well be that my approach is ( in **all** likelyhood )fundamentally flawed but hopefully someone can point me in the correct direction and I can vault another hurdle to the cocoa finishing line!!

Thanks in advance.

- (void)drawRect: (NSRect)dirtyRect {
	
	[self completeTheDrawing: dirtyRect];
	NSRect bounds = [ self bounds];
	NSBezierPath *path = [ NSBezierPath bezierPathWithRect: bounds];
	[[NSColor redColor] set];
	[path fill];
	[[NSColor redColor]set];
	[path setLineWidth:8];
	[path stroke];
	[[NSColor blackColor]set];
	[path setLineWidth:4];
	[path stroke];
	
	
}

 

[chown33]

What kinds of view have a settable color, which they will remember and use to draw in? For example, what has a settable background or foreground color? Subclass that instead of subclassing NSView.

Otherwise, subclass NSView and give it a settable color property. Set that property in the drop-handler. Fill with that color in drawRect.

If this were more complex I'd say create a Model object that has a settable color property. Your view then communicates with its model object to know what color to draw, and your drop-handler communicates with the model object to set the color. It's overkill here, but get used to this pattern, because Model-View-Controller is the way to write things in Cocoa.

 

[mdeh]

Otherwise, subclass NSView and give it a settable color property. Set that property in the drop-handler. Fill with that color in drawRect.

Works beautifully!!!! Thank you.

What kinds of view have a settable color, which they will remember and use to draw in? For example, what has a settable background or foreground color? Subclass that instead of subclassing NSView.

Chown...you have lost me on this one. The only views I see in IB are custom and scroll views. But, perhaps, that is yet to come in Hillegass

If this were more complex I'd say create a Model object that has a settable color property. Your view then communicates with its model object to know what color to draw, and your drop-handler communicates with the model object to set the color. It's overkill here, but get used to this pattern, because Model-View-Controller is the way to write things in Cocoa.

Well, even though I do not have a **formal** controller, I think the way it is set up is indeed with a model, but your point is well taken. I am working my way through mmalc's excellent series on bindings, and I think I am about to be introduced to this in a big way. But, I really do not like to push on ahead without overcoming the little things like this, as there are often concepts hidden in there that are useful.

 

[chown33]

Chown...you have lost me on this one. The only views I see in IB are custom and scroll views. But, perhaps, that is yet to come in Hillegass

Yes, there's much more to come.

What I meant was to look at the classes which are subclasses of NSView, such as NSControl and its subclasses. In a more general sense, look at the Application Kit class hierarchy, and notice all the subclasses of NSView, either direct or by intermediate classes.

 

[mdeh]

Yes, there's much more to come.

What I meant was to look at the classes which are subclasses of NSView, such as NSControl and its subclasses. In a more general sense, look at the Application Kit class hierarchy, and notice all the subclasses of NSView, either direct or by intermediate classes.

Thank you again. Much appreciated.