Value

A value object is a wrapper around some sqlite3 data. It is implemented using a boost::variant, which is a kind of type-safe union. Variants provide a visitor-based API, which is used here for data conversion.

Such a value is either:

• an Integer,
• a Float,
• some Text,
• a Blob,
• or Null (lack of value).

See the types page for more information about those underlying types.

class Value : public boost::variant<Null, Integer, Float, Text, Blob>
{
};

--

Constructors

Name	Description
Value(Integer x)	Creates a Integer Value instance (implicitly).
Value(int x)	Creates a Integer Value instance (implicitly).
Value(Float x)	Creates a Float Value instance (implicitly).
Value(float x)	Creates a Float Value instance (implicitly).
Value(Text x)	Creates a Text Value instance (implicitly).
Value(const char* x)	Creates a Text Value instance (implicitly).
Value(Blob x)	Creates a Blob Value instance (implicitly).
Value(Null x)	Creates a Null Value instance (implicitly).
Value()	Creates a Null Value instance.

--

Value info

Name	Description
bool null() const	Tells whether the object is Null or not.

--

Value conversion

Name	Description
template <typename T> Integer as_integer(T const& cvert) const	Applies visitor, enforces Integer conversion
template <typename T> Float as_float(T const& cvert) const	Applies visitor, enforces Float conversion
template <typename T> Text as_text(T const& cvert) const	Applies visitor, enforces Text conversion
template <typename T> Blob as_blob(T const& cvert) const	Applies visitor, enforces Blob conversion
template <typename T> T as() const	Applies default T converter
Integer as_integer() const	Applies default Integer converter
Float as_float() const	Applies default Float converter
Text as_text() const	Applies default Text converter
Blob as_blob() const	Applies default Blob converter

--

Generic visitor API

Name	Description
template <typename T> typename T::result_type apply(T const& vtor) const	Applies visitor

--

Default converters

Name	Description
static Integer to_integer(Integer const& x)	id
static Integer to_integer(Float const& x)	static cast
static Integer to_integer(Text const& x)	lexical cast
static Integer to_integer(Blob const& x)	to_integer(to_text(x))
static Integer to_integer(Null const& x)	Integer(0)
static Float to_float(Integer const& x)	static cast
static Float to_float(Float const& x)	id
static Float to_float(Text const& x)	lexical cast
static Float to_float(Blob const& x)	to_float(to_text(x))
static Float to_float(Null const& x)	Float(0)
static Text to_text(Integer const& x)	lexical cast
static Text to_text(Float const& x)	lexical cast
static Text to_text(Text const& x)	id
static Text to_text(Blob const& x)	reads blob as char array
static Text to_text(Null const& x)	empty string
static Blob to_blob(Integer const& x)	to_blob(to_text(x))
static Blob to_blob(Float const& x)	to_blob(to_text(x))
static Blob to_blob(Text const& x)	dumps text as char array
static Blob to_blob(Blob const& x)	id
static Blob to_blob(Null const& x)	empty blob