**Library:** Foundation

**Package:** Core

**Header:** Poco/DynamicAny.h

DynamicAny allows to store data of different types and to convert between these types transparently. DynamicAny puts forth the best effort to provide intuitive and reasonable conversion semantics and prevent unexpected data loss, particularly when performing narrowing or signedness conversions of numeric data types.

An attempt to convert or extract from a non-initialized (empty) DynamicAny variable shall result in an exception being thrown.

Loss of signedness is not allowed for numeric values. This means that if an attempt is made to convert the internal value which is a negative signed integer to an unsigned integer type storage, a RangeException is thrown. Overflow is not allowed, so if the internal value is a larger number than the target numeric type size can accomodate, a RangeException is thrown.

Precision loss, such as in conversion from floating-point types to integers or from double to float on platforms where they differ in size (provided internal actual value fits in float min/max range), is allowed.

String truncation is allowed — it is possible to convert between string and character when string length is greater than 1. An empty string gets converted to the char '\0', a non-empty string is truncated to the first character.

Boolean conversion is performed as follows:

A string value "false" (not case sensitive), "0" or "" (empty string) can be converted to a boolean value false, any other string not being false by the above criteria evaluates to true (e.g: "hi" -> true). Integer 0 values are false, everything else is true. Floating point values equal to the minimal FP representation on a given platform are false, everything else is true.

Arithmetic operations with POD types as well as between DynamicAny's are supported, subject to following limitations:

- for std::string and const char* values, only '+' and '+=' operations are supported

- for integral and floating point numeric values, following operations are supported:

'+', '+=', '-', '-=', '*', '*=' , '/' and '/='

- for integral values, following operations are supported:

prefix and postfix increment (++) and decement (--)

- for all other types, InvalidArgumentException is thrown upon attempt of an arithmetic operation

A DynamicAny can be created from and converted to a value of any type for which a specialization of DynamicAnyHolderImpl is available. For supported types, see DynamicAnyHolder documentation.

**Member Functions: **convert, empty, extract, isArray, isEmpty, isInteger, isNumeric, isSigned, isString, operator !, operator !=, operator &&, operator *, operator *=, operator +, operator ++, operator +=, operator -, operator --, operator -=, operator /, operator /=, operator <, operator <=, operator =, operator ==, operator >, operator >=, operator T, operator [], operator ||, swap, type

DynamicAny();

Creates an empty DynamicAny.

template < typename T > DynamicAny(

const T & val

);

Creates the DynamicAny from the given value.

DynamicAny(

const char * pVal

);

DynamicAny(

const DynamicAny & other

);

Copy constructor.

~DynamicAny();

Destroys the DynamicAny.

template < typename T > void convert(

T & val

) const;

Invoke this method to perform a safe conversion.

Example usage:

DynamicAny any("42"); int i; any.convert(i);

Throws a RangeException if the value does not fit into the result variable. Throws a NotImplementedException if conversion is not available for the given type. Throws InvalidAccessException if DynamicAny is empty.

template < typename T > T convert() const;

Invoke this method to perform a safe conversion.

Example usage:

DynamicAny any("42"); int i = any.convert<int>();

Throws a RangeException if the value does not fit into the result variable. Throws a NotImplementedException if conversion is not available for the given type. Throws InvalidAccessException if DynamicAny is empty.

void empty();

Empties DynamicAny.

template < typename T > const T & extract() const;

Returns a const reference to the actual value.

Must be instantiated with the exact type of the stored value, otherwise a BadCastException is thrown. Throws InvalidAccessException if DynamicAny is empty.

bool isArray() const;

Returns true if DynamicAny represents a vector

bool isEmpty() const;

Returns true if empty.

bool isInteger() const;

Returns true if stored value is integer.

bool isNumeric() const;

Returns true if stored value is numeric. Returns false for numeric strings (e.g. "123" is string, not number)

bool isSigned() const;

Returns true if stored value is signed.

bool isString() const;

Returns true if stored value is std::string.

bool operator ! () const;

Logical NOT operator.

template < typename T > bool operator != (

const T & other

) const;

Inequality operator

bool operator != (

const DynamicAny & other

) const;

Inequality operator overload for DynamicAny

bool operator != (

const char * other

) const;

Inequality operator overload for const char*

template < typename T > bool operator && (

const T & other

) const;

Logical AND operator

bool operator && (

const DynamicAny & other

) const;

Logical AND operator operator overload for DynamicAny

template < typename T > const DynamicAny operator * (

const T & other

) const;

Multiplication operator for multiplying DynamicAny with POD

const DynamicAny operator * (

const DynamicAny & other

) const;

Multiplication operator overload for DynamicAny

template < typename T > DynamicAny & operator *= (

const T & other

);

Multiplication assignment operator

DynamicAny & operator *= (

const DynamicAny & other

);

Multiplication assignment operator overload for DynamicAny

template < typename T > const DynamicAny operator + (

const T & other

) const;

Addition operator for adding POD to DynamicAny

const DynamicAny operator + (

const DynamicAny & other

) const;

Addition operator specialization for DynamicAny

const DynamicAny operator + (

const char * other

) const;

Addition operator specialization for adding const char* to DynamicAny

DynamicAny & operator ++ ();

Pre-increment operator

const DynamicAny operator ++ (

int

);

Post-increment operator

template < typename T > DynamicAny & operator += (

const T & other

);

Addition assignment operator for addition/assignment of POD to DynamicAny.

DynamicAny & operator += (

const DynamicAny & other

);

Addition assignment operator overload for DynamicAny

DynamicAny & operator += (

const char * other

);

Addition assignment operator overload for const char*

template < typename T > const DynamicAny operator - (

const T & other

) const;

Subtraction operator for subtracting POD from DynamicAny

const DynamicAny operator - (

const DynamicAny & other

) const;

Subtraction operator overload for DynamicAny

DynamicAny & operator -- ();

Pre-decrement operator

const DynamicAny operator -- (

int

);

Post-decrement operator

template < typename T > DynamicAny & operator -= (

const T & other

);

Subtraction assignment operator

DynamicAny & operator -= (

const DynamicAny & other

);

Subtraction assignment operator overload for DynamicAny

template < typename T > const DynamicAny operator / (

const T & other

) const;

Division operator for dividing DynamicAny with POD

const DynamicAny operator / (

const DynamicAny & other

) const;

Division operator overload for DynamicAny

template < typename T > DynamicAny & operator /= (

const T & other

);

Division assignment operator

DynamicAny & operator /= (

const DynamicAny & other

);

Division assignment operator specialization for DynamicAny

template < typename T > bool operator < (

const T & other

) const;

Less than operator

bool operator < (

const DynamicAny & other

) const;

Less than operator overload for DynamicAny

template < typename T > bool operator <= (

const T & other

) const;

Less than or equal operator

bool operator <= (

const DynamicAny & other

) const;

Less than or equal operator overload for DynamicAny

template < typename T > DynamicAny & operator = (

const T & other

);

Assignment operator for assigning POD to DynamicAny

DynamicAny & operator = (

const DynamicAny & other

);

Assignment operator specialization for DynamicAny

template < typename T > bool operator == (

const T & other

) const;

Equality operator

bool operator == (

const char * other

) const;

Equality operator overload for const char*

bool operator == (

const DynamicAny & other

) const;

Equality operator overload for DynamicAny

template < typename T > bool operator > (

const T & other

) const;

Greater than operator

bool operator > (

const DynamicAny & other

) const;

Greater than operator overload for DynamicAny

template < typename T > bool operator >= (

const T & other

) const;

Greater than or equal operator

bool operator >= (

const DynamicAny & other

) const;

Greater than or equal operator overload for DynamicAny

template < typename T > operator T() const;

Safe conversion operator for implicit type conversions. If the requested type T is same as the type being held, the operation performed is direct extraction, otherwise it is the conversion of the value from type currently held to the one requested.

Throws a RangeException if the value does not fit into the result variable. Throws a NotImplementedException if conversion is not available for the given type. Throws InvalidAccessException if DynamicAny is empty.

template < typename T > DynamicAny & operator[] (

T n

);

Index operator, only use on DynamicAnys where isArray returns true! In all other cases InvalidAccessException is thrown.

template < typename T > const DynamicAny & operator[] (

T n

) const;

const Index operator, only use on DynamicAnys where isArray returns true! In all other cases InvalidAccessException is thrown.

template < typename T > bool operator || (

const T & other

) const;

Logical OR operator

bool operator || (

const DynamicAny & other

) const;

Logical OR operator operator overload for DynamicAny

void swap(

DynamicAny & other

);

Swaps the content of the this DynamicAny with the other DynamicAny.

const std::type_info & type() const;

Returns the type information of the stored content.