NSPlaceholders protocol provides an interface that allows an object to register default placeholders that will be displayed for a binding, when no other placeholder has been specified. Individual placeholder values can be specified for each of the marker objects (described in Selection Markers), as well as when the property is
- macOS 10.3+
Placeholders are used when a property of an instance of the receiving class is accessed through a key value coding compliant method, and returns
nil or a specialized marker.