union keyword

union keyword

Declares a union

---

  class-key  := union 

The union keyword declares an aggregate type, similar to a struct , but the union object can store only one member at a time. The storage for all members overlaps. A union can have member functions (including constructors and destructors) but not virtual member functions. A union cannot be or have a base class. Union members cannot be static or references. Data members cannot have constructors, a destructor, copy-assignment operators, virtual functions, or virtual base classes. An initializer for a union can initialize only its first member.

See class for the syntax rules.

Example

 enum kind { integer, real, text }; struct data {   kind data_kind;   data(int i) : data_kind(integer), integerval(i) {}   data(double d) : data_kind(real), realval(d) {}  union  {     int integerval;     double realval;   }; }; 

See Also

class , struct , Chapter 2, Chapter 6