Best way to change the background color for an NSView

If you are a storyboard lover, here is a way that you don't need any line of code.

Add NSBox as a subview to NSView and adjust NSBox's frame as the same with NSView.

In Storyboard or XIB change Title position to None, Box type to Custom, Border Type to "None", and Border color to whatever you like.

Here is a screenshot:

This is the result:

Yeah, your own answer was right. You could also use Cocoa methods:

- (void)drawRect:(NSRect)dirtyRect {
    // set any NSColor for filling, say white:
    [[NSColor whiteColor] setFill];
    NSRectFill(dirtyRect);
    [super drawRect:dirtyRect];
}

In Swift:

class MyView: NSView {

    override func draw(_ dirtyRect: NSRect) {
        super.draw(dirtyRect)

        // #1d161d
        NSColor(red: 0x1d/255, green: 0x16/255, blue: 0x1d/255, alpha: 1).setFill()
        dirtyRect.fill()
    }

}

An easy, efficient solution is to configure the view to use a Core Animation layer as its backing store. Then you can use -[CALayer setBackgroundColor:] to set the background color of the layer.

- (void)awakeFromNib {
   self.wantsLayer = YES;  // NSView will create a CALayer automatically
}

- (BOOL)wantsUpdateLayer {
   return YES;  // Tells NSView to call `updateLayer` instead of `drawRect:`
}

- (void)updateLayer {
   self.layer.backgroundColor = [NSColor colorWithCalibratedRed:0.227f 
                                                          green:0.251f 
                                                           blue:0.337 
                                                          alpha:0.8].CGColor;
}

That’s it!