How does one use SwiftUI's ToolbarItemGroup?

Question

I clear don't understand the meaning of the definition syntax for SwiftUI because I can't figure out how one would use ToolbarItemGroup.

I can define a toolbar with toolbar items like this:

.toolbar {
            
            ToolbarItem {
                Button("200%", action: zoom200).foregroundColor(controller.scale == 2.0 ? selectedButtonColor : defaultButtonColor)
            }
            ToolbarItem {
                Button("100%", action: zoom100).foregroundColor(controller.scale == 1.0 ? selectedButtonColor : defaultButtonColor)
            }
}

But have been unable to get ToolbarItemGroup to work. Logically I would have expected something like this:

.toolbar {
   ToolbarItemGroup {
            
         ToolbarItem {
                Button("200%", action: zoom200).foregroundColor(controller.scale == 2.0 ? selectedButtonColor : defaultButtonColor)
            }
         ToolbarItem {
                Button("100%", action: zoom100).foregroundColor(controller.scale == 1.0 ? selectedButtonColor : defaultButtonColor)
            }
   }
   ToolbarItemGroup {
         ToolbarItem {
                Button("Open", action: open)
            }
         ToolbarItem {
                Button("Close", action: close)
            }
   }
}

Answer 1

ToolbarItemGroup is designed to group views in the same toolbar. It removes the need for explicit usage of ToolbarItem, as both conform to ToolbarContent.

e.g.

.toolbar {
  ToolbarItemGroup {
    Button("200%",  action: zoom200)
      .foregroundColor(controller.scale == 2.0 ? selectedButtonColor : defaultButtonColor)
    Button("100%", action: zoom100)
      .foregroundColor(controller.scale == 1.0 ? selectedButtonColor : defaultButtonColor)
  }
  ToolbarItemGroup(placement: .bottomBar) {
    Spacer()
    Button("Open", action: open)
    Spacer()
    Button("Close", action: close)
    Spacer()
  }
}

It's also the only way I know of to get Spacers to work, between toolbar items.