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228 lines
7.1 KiB
C++
228 lines
7.1 KiB
C++
//
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// DynamicAny.h
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//
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// $Id: //poco/Main/Foundation/include/Poco/DynamicAny.h#9 $
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//
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// Library: Foundation
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// Package: Core
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// Module: DynamicAny
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//
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// Definition of the DynamicAny class.
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//
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// Copyright (c) 2007, Applied Informatics Software Engineering GmbH.
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// and Contributors.
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//
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// Permission is hereby granted, free of charge, to any person or organization
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// obtaining a copy of the software and accompanying documentation covered by
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// this license (the "Software") to use, reproduce, display, distribute,
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// execute, and transmit the Software, and to prepare derivative works of the
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// Software, and to permit third-parties to whom the Software is furnished to
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// do so, all subject to the following:
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//
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// The copyright notices in the Software and this entire statement, including
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// the above license grant, this restriction and the following disclaimer,
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// must be included in all copies of the Software, in whole or in part, and
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// all derivative works of the Software, unless such copies or derivative
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// works are solely in the form of machine-executable object code generated by
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// a source language processor.
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//
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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// FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
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// SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
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// FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
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// ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
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// DEALINGS IN THE SOFTWARE.
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//
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#ifndef Foundation_DynamicAny_INCLUDED
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#define Foundation_DynamicAny_INCLUDED
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#include "Poco/Foundation.h"
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#include "Poco/DynamicAnyHolder.h"
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#include <typeinfo>
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namespace Poco {
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class Foundation_API DynamicAny
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/// DynamicAny allows to store data of different types and to convert between these types transparently.
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/// DynamicAny puts forth the best effort to provide intuitive and reasonable conversion semantics and prevent
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/// unexpected data loss, particularly when performing narrowing or signedness conversions of numeric data types.
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///
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/// Loss of signedness is not allowed for numeric values. This means that if an attempt is made to convert
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/// the internal value which is a negative signed integer to an unsigned integer type storage, a RangeException is thrown.
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/// Overflow is not allowed, so if the internal value is a larger number than the target numeric type size can accomodate,
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/// a RangeException is thrown.
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///
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/// Precision loss, such as in conversion from floating-point types to integers or from double to float on platforms
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/// where they differ in size (provided internal actual value fits in float min/max range), is allowed.
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///
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/// String truncation is allowed -- it is possible to convert between string and character when string length is
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/// greater than 1. An empty string gets converted to the char '\0', a non-empty string is truncated to the first character.
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///
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/// Bolean conversion are performed as follows:
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///
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/// A string value "false" (not case sensitive) or "0" can be converted to a boolean value false, any other string
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/// not being false by the above criteria evaluates to true (e.g: "hi" -> true).
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/// Integer 0 values are false, everything else is true.
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/// Floating point values equal to the minimal FP representation on a given platform are false, everything else is true.
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///
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/// A DynamicAny can be created from and converted to a value of any type for which a specialization of
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/// DynamicAnyHolderImpl is available. For supported types, see DynamicAnyHolder documentation.
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{
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public:
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DynamicAny();
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/// Creates a DynamicAny holding an int with value 0.
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template <typename T>
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DynamicAny(const T &val):
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_pHolder(new DynamicAnyHolderImpl<T>(val))
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/// Creates the DynamicAny from the given value.
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{
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}
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DynamicAny(const char* pVal);
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// Convenience constructor for const char* which gets mapped to a std::string internally, i.e. pVal is deep-copied.
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DynamicAny(const DynamicAny& other);
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/// Copy constructor.
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~DynamicAny();
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/// Destroys the DynamicAny.
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void swap(DynamicAny& other);
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/// Swaps the content of the this DynamicAny with the other DynamicAny.
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template <typename T>
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void convert(T& val) const
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/// Invoke this method to perform a safe conversion.
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///
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/// Example usage:
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/// DynamicAny any("42");
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/// int i;
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/// any.convert(i);
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///
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/// Throws a RangeException if the value does not fit
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/// into the result variable.
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/// Throws a NotImplementedException if conversion is
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/// not available for the given type.
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{
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_pHolder->convert(val);
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}
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template <typename T>
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T convert() const
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/// Invoke this method to perform a safe conversion.
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///
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/// Example usage:
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/// DynamicAny any("42");
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/// int i = any.convert<int>();
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///
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/// Throws a RangeException if the value does not fit
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/// into the result variable.
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/// Throws a NotImplementedException if conversion is
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/// not available for the given type.
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{
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T result;
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_pHolder->convert(result);
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return result;
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}
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template <typename T>
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operator T() const
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/// Safe conversion operator for implicit type
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/// conversions.
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///
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/// Throws a RangeException if the value does not fit
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/// into the result variable.
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/// Throws a NotImplementedException if conversion is
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/// not available for the given type.
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{
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T result;
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_pHolder->convert(result);
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return result;
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}
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template <typename T>
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const T& extract() const
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/// Returns a const reference to the actual value.
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///
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/// Must be instantiated with the exact type of
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/// the stored value, otherwise a BadCastException
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/// is thrown.
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{
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DynamicAnyHolderImpl<T>* pHolder = dynamic_cast<DynamicAnyHolderImpl<T>*>(_pHolder);
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if (pHolder)
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return pHolder->value();
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else
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throw BadCastException();
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}
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DynamicAny& operator = (const DynamicAny& other)
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/// Assignment operator
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{
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DynamicAny tmp(other);
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swap(tmp);
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return *this;
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}
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template <typename T>
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DynamicAny& operator = (const T& other)
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/// Assignment operator
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{
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DynamicAny tmp(other);
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swap(tmp);
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return *this;
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}
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template <typename T>
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bool operator == (const T& other)
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/// Equality operator
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{
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T value;
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_pHolder->convert(value);
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return value == other;
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}
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bool operator == (const char* other)
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/// Equality operator
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{
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std::string value;
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_pHolder->convert(value);
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return value == other;
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}
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template <typename T>
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bool operator != (const T& other)
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/// Inequality operator
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{
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T value;
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_pHolder->convert(value);
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return value != other;
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}
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bool operator != (const char* other)
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/// Inequality operator
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{
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std::string value;
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_pHolder->convert(value);
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return value != other;
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}
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const std::type_info& type() const;
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/// Returns the type information of the stored content.
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private:
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DynamicAnyHolder* _pHolder;
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};
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} // namespace Poco
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#endif // Foundation_DynamicAny_INCLUDED
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