SC::TaggedUnion< Union > Struct Template Reference

Type safe union with an enum type, where each type has an associated enum value. More...

#include <TaggedUnion.h>

Classes
struct	EnumToType
	Extracts type T corresponding to enumeration wantedEnum at compile time. More...
struct	EnumToType< wantedEnum, 0 >

Public Types
using	EnumType = typename TypeAt< 0 >::enumType

Public Member Functions
	~TaggedUnion ()
	Destroys the TaggedUnion object. More...
	TaggedUnion (const TaggedUnion &other)
	Copy constructor. More...
	TaggedUnion (TaggedUnion &&other)
	Move constructor. More...
TaggedUnion &	operator= (const TaggedUnion &other)
	Copy assignment operator. More...
TaggedUnion &	operator= (TaggedUnion &&other)
	Move assignment operator. More...
EnumType	getType () const
	Returns enumeration value of currently active union type. More...
void	setType (EnumType newType)
	Sets the currently active type at runtime, destructing and (default) constructing the new type. More...
bool	operator== (const TaggedUnion &other) const
template<EnumType wantedType, typename U >
void	assign (U &&other)
	Assigns a compile time known enum type with an object U. More...
template<EnumType wantedType>
TypeAt< EnumToType< wantedType >::index >::type &	changeTo ()
	Changes current active type in union to a different one. More...
template<EnumType wantedType>
TypeAt< EnumToType< wantedType >::index >::type *	field ()
	Get a pointer to currently active field. More...
template<EnumType wantedType>
const TypeAt< EnumToType< wantedType >::index >::type *	field () const
	Get a pointer to currently active field. More...

Static Public Attributes
static constexpr auto	NumTypes = Union::FieldsTypes::size

Detailed Description

template<typename Union>
struct SC::TaggedUnion< Union >

Type safe union with an enum type, where each type has an associated enum value.

Template Parameters

Union

with FieldTypes = TypeList<TaggedType<EnumType, EnumValue, Type>, ...>

Example:

namespace SC
{
struct TaggedUnionTest;
 
// Create an arbitrary enumeration with some values
enum TestType
{
    TypeString = 10,
    TypeInt    = 110,
};
 
// Create the union definition containing a FieldTypes nested type
struct TestUnion
{
    // Helper to save some typing
    template <TestType E, typename T>
    using Tag = TaggedType<TestType, E, T>;
 
    // FieldsTypes MUST be defined to be a TypeList of TaggedType(s)
    using FieldsTypes = TypeTraits::TypeList< // List all TargetType associations
        Tag<TypeString, String>,              // Associate TypeString with String
        Tag<TypeInt, int>>;                   // Associate TypeInt with init
};
 
void taggedUnionUsageSnippet(Console& console)
{
    // Create the tagged union on the TestUnion definition
    TaggedUnion<TestUnion> test; // default initialized to first type (String)
 
    // Access / Change type
    String* ptr = test.field<TypeString>();
    if (ptr) // If TypeString is not active type, ptr will be == nullptr
    {
        *ptr = "SomeValue";
    }
    test.changeTo<TypeInt>() = 2; // Change active type to TypeInt (compile time known)
 
    // Switch on currently active type (TypeInt)
    switch (test.getType())
    {
    case TypeString: console.print("String = {}", *test.field<TypeString>()); break;
    case TypeInt: console.print("Int = {}", *test.field<TypeInt>()); break;
    }
 
    // Set current active type at runtime back to TypeString
    test.setType(TypeString);
    *test.field<TypeString>() = "Some new string";
}
} // namespace SC

Constructor & Destructor Documentation

~TaggedUnion()

template<typename Union >

SC::TaggedUnion< Union >::~TaggedUnion ( )

inline

Destroys the TaggedUnion object.

TaggedUnion() [1/2]

template<typename Union >

SC::TaggedUnion< Union >::TaggedUnion ( const TaggedUnion< Union > &  other )

inline

Copy constructor.

Parameters

other

Another tagged union

TaggedUnion() [2/2]

template<typename Union >

SC::TaggedUnion< Union >::TaggedUnion ( TaggedUnion< Union > &&  other )

inline

Move constructor.

Parameters

other

Another tagged union

Member Function Documentation

assign()

template<typename Union >

template<EnumType wantedType, typename U >

void SC::TaggedUnion< Union >::assign ( U &&  other )

inline

Assigns a compile time known enum type with an object U.

Template Parameters

U	Type of object to be assigned.
wantedType	Compile time known enum type

Parameters

other

object to be assigned (move / copy)

changeTo()

template<typename Union >

template<EnumType wantedType>

TypeAt< EnumToType< wantedType >::index >::type & SC::TaggedUnion< Union >::changeTo ( )

inline

Changes current active type in union to a different one.

Template Parameters

wantedType

Compile time know enum value associated to wanted type

Returns

A reference to the wanted type. If wantedType is not the active type, a new value will be default initialized

Note

Return type is made explicit instead of using auto to help intellisense deducing type

field() [1/2]

template<typename Union >

template<EnumType wantedType>

TypeAt< EnumToType< wantedType >::index >::type * SC::TaggedUnion< Union >::field ( )

inline

Get a pointer to currently active field.

Template Parameters

wantedType

Compile time know enum value associated to wanted type

Returns

A pointer to currently active field or nullptr if wantedType doesn't match currently active type.

Note

Return type is made explicit instead of using auto to help intellisense deducing type

field() [2/2]

template<typename Union >

template<EnumType wantedType>

const TypeAt< EnumToType< wantedType >::index >::type * SC::TaggedUnion< Union >::field ( ) const

inline

Get a pointer to currently active field.

Template Parameters

wantedType

Compile time know enum value associated to wanted type

Returns

A pointer to currently active field or nullptr if wantedType doesn't match currently active type.

Note

Return type is made explicit instead of using auto to help intellisense deducing type

getType()

template<typename Union >

EnumType SC::TaggedUnion< Union >::getType ( ) const

inline

Returns enumeration value of currently active union type.

operator=() [1/2]

template<typename Union >

TaggedUnion & SC::TaggedUnion< Union >::operator= ( const TaggedUnion< Union > &  other )

inline

Copy assignment operator.

Parameters

other

Another tagged union

operator=() [2/2]

template<typename Union >

TaggedUnion & SC::TaggedUnion< Union >::operator= ( TaggedUnion< Union > &&  other )

inline

Move assignment operator.

Parameters

other

Another tagged union

setType()

template<typename Union >

void SC::TaggedUnion< Union >::setType ( EnumType  newType )

inline

Sets the currently active type at runtime, destructing and (default) constructing the new type.

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The documentation for this struct was generated from the following file:

• TaggedUnion.h