Selects all items in the collection view, if doing so is possible.
- macOS 10.11+
The object that requested the action. You may specify
nilfor this property.
This method works only when the
allows properties are both
true. If either property is set to
false, this method quietly does nothing and any connected menu item is disabled.
This method consults the delegate object regarding the selection. Specifically, it calls the delegate’s
collection method to see if the items should be selected. For any items that are selected, it calls the