Best practice for resize window with animation using ToolBar on Cocoa

I'm wondering what's the best practice to resize a window when Toolbar changes.

I'm trying to get this effect (animated) when a Toolbar selected option changes.

Any ideas?

Thank you for your help! :)

Here's my commonly used method:

After clicking the new toolbar item, firstly get the frame size of the new subview to be added, then change window's frame with animation.

Demo (just change height, but you can add support to change width):

- (void)switchToTabView:(NSView *)settingView withAnimation:(BOOL)animation
{
    NSView *windowView = self.window.contentView;
    for (NSView *view in windowView.subviews) {
        [view removeFromSuperview];
    }

    CGFloat oldHeight = windowView.frame.size.height;

    [windowView addSubview:settingView];
    CGFloat newHeight = settingView.frame.size.height;

    CGFloat delta = newHeight - oldHeight;

    NSPoint origin = settingView.frame.origin;
    origin.y -= delta;
    [settingView setFrameOrigin:origin];

    NSRect frame = self.window.frame;
    frame.size.height += delta;
    frame.origin.y -= delta;
    [self.window setFrame:frame display:YES animate:animation];
}