lsst::afw::typehandling::PolymorphicValue Class Reference

Container that passes Storable objects by value while preserving type. More...

#include <PolymorphicValue.h>

Public Member Functions
	PolymorphicValue (Storable const &value)
	Create a new object containing a copy of a Storable. More...
	~PolymorphicValue () noexcept
bool	empty () const noexcept
	Check whether this object contains a Storable. More...
std::size_t	hash_value () const
	Return a hash of this object (optional operation). More...
	PolymorphicValue (PolymorphicValue const &other)
	Try to copy a PolymorphicValue. More...
	PolymorphicValue (PolymorphicValue &&other) noexcept
	Try to copy a PolymorphicValue. More...
PolymorphicValue &	operator= (PolymorphicValue const &other)
	Try to assign a PolymorphicValue. More...
PolymorphicValue &	operator= (PolymorphicValue &&other) noexcept
	Try to assign a PolymorphicValue. More...
void	swap (PolymorphicValue &other) noexcept
	Exchange the contents of this container and another. More...
	operator Storable & ()
	Return a reference to the internal Storable, if one exists. More...
	operator Storable const & () const
	Return a reference to the internal Storable, if one exists. More...
Storable &	get ()
	Return a reference to the internal Storable, if one exists. More...
Storable const &	get () const
	Return a reference to the internal Storable, if one exists. More...
bool	operator== (PolymorphicValue const &other) const noexcept
	Test whether the contained Storables are equal. More...
bool	operator!= (PolymorphicValue const &other) const noexcept
	Test whether the contained Storables are equal. More...

Related Functions
(Note that these are not member functions.)
void	swap (PolymorphicValue &lhs, PolymorphicValue &rhs) noexcept
	Swap specialization for PolymorphicValue. More...

Detailed Description

Container that passes Storable objects by value while preserving type.

This class is implicitly convertible to and from a reference to Storable, but behaves like a value: changing the internal Storable changes the object's state, and copying the object creates a new Storable.

Note

While a PolymorphicValue is always initialized with a Storable, it may become empty if it is the source of a move-construction or move-assignment. Conversion of an empty value to Storable& throws.

Definition at line 52 of file PolymorphicValue.h.

Constructor & Destructor Documentation

PolymorphicValue() [1/3]

lsst::afw::typehandling::PolymorphicValue::PolymorphicValue

(

Storable const &

value

)

Create a new object containing a copy of a Storable.

Parameters

value

the value to copy into a PolymorphicValue

Definition at line 33 of file PolymorphicValue.cc.

: _value(value.cloneStorable()) {}

~PolymorphicValue()

lsst::afw::typehandling::PolymorphicValue::~PolymorphicValue ( )

defaultnoexcept

PolymorphicValue() [2/3]

lsst::afw::typehandling::PolymorphicValue::PolymorphicValue

(

PolymorphicValue const &

other

)

Try to copy a PolymorphicValue.

Parameters

other

the PolymorphicValue to copy.

Exceptions

UnsupportedOperationException

Thrown if a copy is required and the object in other does not implement Storable::cloneStorable.

Definition at line 39 of file PolymorphicValue.cc.

        : _value(other._value ? other._value->cloneStorable() : nullptr) {}

PolymorphicValue() [3/3]

lsst::afw::typehandling::PolymorphicValue::PolymorphicValue ( PolymorphicValue &&  other )

defaultnoexcept

Try to copy a PolymorphicValue.

Parameters

other

the PolymorphicValue to copy.

Exceptions

UnsupportedOperationException

Thrown if a copy is required and the object in other does not implement Storable::cloneStorable.

Member Function Documentation

empty()

bool lsst::afw::typehandling::PolymorphicValue::empty ( ) const

noexcept

Check whether this object contains a Storable.

Returns

true if this object has no Storable, false otherwise

Definition at line 62 of file PolymorphicValue.cc.

{ return !_value; }

get() [1/2]

Storable & lsst::afw::typehandling::PolymorphicValue::get

(

)

Return a reference to the internal Storable, if one exists.

Returns

a reference to the internal object

Exceptions

pex::exceptions::LogicError

Thrown if this object is empty.

Definition at line 66 of file PolymorphicValue.cc.

                                {
    // Both casts are safe; see Effective C++, Item 3
    return const_cast<Storable&>(static_cast<PolymorphicValue const&>(*this).get());
}

get() [2/2]

Storable const & lsst::afw::typehandling::PolymorphicValue::get

(

)

const

Return a reference to the internal Storable, if one exists.

Returns

a reference to the internal object

Exceptions

pex::exceptions::LogicError

Thrown if this object is empty.

Definition at line 70 of file PolymorphicValue.cc.

                                            {
    if (_value) {
        return *_value;
    } else {
        throw LSST_EXCEPT(pex::exceptions::LogicError, "Dereferenced empty PolymorphicValue.");
    }
}

hash_value()

std::size_t lsst::afw::typehandling::PolymorphicValue::hash_value

(

)

const

Return a hash of this object (optional operation).

Exceptions

UnsupportedOperationException

Thrown if the internal Storable is not hashable.

Definition at line 87 of file PolymorphicValue.cc.

{ return std::hash<Storable>()(get()); }

operator Storable &()

lsst::afw::typehandling::PolymorphicValue::operator Storable &

(

)

Return a reference to the internal Storable, if one exists.

Returns

a reference to the internal object

Exceptions

pex::exceptions::LogicError

Thrown if this object is empty.

Definition at line 64 of file PolymorphicValue.cc.

{ return get(); }

operator Storable const &()

lsst::afw::typehandling::PolymorphicValue::operator Storable const &

(

)

const

Return a reference to the internal Storable, if one exists.

Returns

a reference to the internal object

Exceptions

pex::exceptions::LogicError

Thrown if this object is empty.

operator!=()

bool lsst::afw::typehandling::PolymorphicValue::operator!= ( PolymorphicValue const &  other ) const

inlinenoexcept

Test whether the contained Storables are equal.

Empty PolymorphicValues compare equal to each other and unequal to any non-empty PolymorphicValue.

Definition at line 130 of file PolymorphicValue.h.

{ return !(*this == other); }

operator=() [1/2]

PolymorphicValue & lsst::afw::typehandling::PolymorphicValue::operator=

(

PolymorphicValue const &

other

)

Try to assign a PolymorphicValue.

To preserve the run-time type of the object in other, this method swaps (and possibly copies) the Storables instead of relying on the Storable's operator=.

Parameters

other

the PolymorphicValue to overwrite this value with.

Exceptions

UnsupportedOperationException

Thrown if a copy is required and the object in other does not implement Storable::cloneStorable.

Definition at line 43 of file PolymorphicValue.cc.

                                                                           {
    if (other._value) {
        _value = other._value->cloneStorable();
    } else {
        _value.reset();
    }
    return *this;
}

operator=() [2/2]

PolymorphicValue & lsst::afw::typehandling::PolymorphicValue::operator= ( PolymorphicValue &&  other )

noexcept

Try to assign a PolymorphicValue.

To preserve the run-time type of the object in other, this method swaps (and possibly copies) the Storables instead of relying on the Storable's operator=.

Parameters

other

the PolymorphicValue to overwrite this value with.

Exceptions

UnsupportedOperationException

Thrown if a copy is required and the object in other does not implement Storable::cloneStorable.

Definition at line 51 of file PolymorphicValue.cc.

                                                                               {
    using std::swap;
    swap(_value, other._value);
    return *this;
}

operator==()

bool lsst::afw::typehandling::PolymorphicValue::operator== ( PolymorphicValue const &  other ) const

noexcept

Test whether the contained Storables are equal.

Empty PolymorphicValues compare equal to each other and unequal to any non-empty PolymorphicValue.

Definition at line 78 of file PolymorphicValue.cc.

                                                                              {
    if (!empty() && !other.empty()) {
        return get().equals(other.get());
    } else {
        // At least one pointer is null; pointer comparison has desired behavior
        return _value == other._value;
    }
}

swap()

void lsst::afw::typehandling::PolymorphicValue::swap ( PolymorphicValue &  other )

noexcept

Exchange the contents of this container and another.

Definition at line 57 of file PolymorphicValue.cc.

                                                            {
    using std::swap;
    swap(_value, other._value);
}

Friends And Related Function Documentation

swap()

void swap ( PolymorphicValue &  lhs, PolymorphicValue &  rhs  )

related

Swap specialization for PolymorphicValue.

Definition at line 152 of file PolymorphicValue.h.

{ lhs.swap(rhs); }

---

The documentation for this class was generated from the following files:

• /j/snowflake/release/lsstsw/stack/Linux64/afw/19.0.0-4-ga671dab3b+1/include/lsst/afw/typehandling/PolymorphicValue.h
• /j/snowflake/release/lsstsw/stack/Linux64/afw/19.0.0-4-ga671dab3b+1/src/typehandling/PolymorphicValue.cc