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
