For automation interface information about the Union property (Is Union through the automation interface), see the automation interface topic for the owning item type in the Related Topics.

This property specifies that a Class or Signal is a Union. For code generation purposes (including C, C++ and Ada), this means that it will be coded as a Union instead of a Class or Struct. When selected {union} appears below the Name of the Class or Signal on the Class Diagram.

A Union is a variable that can store objects of different types and sizes. A Union can store only one object at any given time, and it is not aware of what object type it is storing. The list of objects a Union can store corresponds to the Attributes and Roles on the Class or Signal. A Union should not own any Operations.

By default, the Union check box is cleared.

This property is set on the Options tab of a Class' or Signal's Property Pages. The Union check box is available only if the Structure, Template and Template Specialization check boxes are cleared.

The following section provides information about the items and diagrams for which Union is a property. For more information about an item or diagram, click it.