mtcore::Optional< T > Struct Template Reference

Represents a value that may or may not exist (an "Optional" value) Similar concept to std::optional, but different implementation and additional nicety methods which makes this a better alternative for simple loop-based iteration (via copy_if_present and move_if_present) More...

#include <optional.hpp>

Inheritance diagram for mtcore::Optional< T >:

Public Member Functions
	Optional ()
	Creates an empty Optional.
	Optional (const T &value)
	Creates an Optional from a value.
	Optional (T &&value)
	Creates an Optional from a value.
bool	operator== (const Optional &other) const noexcept
	Checks if value is equal to another Optional.
bool	operator== (const T &other) const noexcept
	Checks if value is equal to a non-Optional value.
T	value_or (const T &def) const noexcept
	Returns the value in the optional, or a default value if the optional is empty.
bool	has_value () const noexcept
bool	empty () const noexcept
T &	value () noexcept
const T &	value () const noexcept
bool	copy_if_present (std::remove_const_t< T > &out) const noexcept
	Copies a value to a reference output destination if a value is present Designed to be used by simple iterators as part of a while loop on a next() method Example:
bool	move_if_present (T &out) noexcept
	Moves a value to a reference output destination if a value is present.
const T &	operator* () const
	Dereferences the internal value.
const T *	operator-> () const
	Dereferences the internal value.
T &	operator* ()
	Dereferences the internal value.
T *	operator-> ()
	Dereferences the internal value.

Detailed Description

template<typename T>
struct mtcore::Optional< T >

Represents a value that may or may not exist (an "Optional" value) Similar concept to std::optional, but different implementation and additional nicety methods which makes this a better alternative for simple loop-based iteration (via copy_if_present and move_if_present)

Definition at line 235 of file optional.hpp.

Constructor & Destructor Documentation

Optional() [1/3]

template<typename T>

mtcore::Optional< T >::Optional ( )

inline

Creates an empty Optional.

Definition at line 243 of file optional.hpp.

: v(std::monostate{}) { ensure(!has_value()); }

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Optional() [2/3]

template<typename T>

mtcore::Optional< T >::Optional ( const T & value )

inline

Creates an Optional from a value.

Definition at line 248 of file optional.hpp.

: v(value) {}

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Optional() [3/3]

template<typename T>

mtcore::Optional< T >::Optional ( T && value )

inline

Creates an Optional from a value.

Definition at line 253 of file optional.hpp.

: v(std::forward<T>(value)) {}

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Member Function Documentation

copy_if_present()

template<typename T>

bool mtcore::Optional< T >::copy_if_present ( std::remove_const_t< T > & out ) const

inlinenodiscardnoexcept

Copies a value to a reference output destination if a value is present Designed to be used by simple iterators as part of a while loop on a next() method Example:

auto iter = myCollection.iter();
T myVal;
while (iter.next().copy_if_present(myVal)) {
   // loop contents
}

Parameters

out	Where to put the destination

Returns

true if a value was copied, false otherwise

Definition at line 327 of file optional.hpp.

                                                                                 {
      if (has_value()) {
        out = std::get<T>(v);
        return true;
      }
      return false;
    }

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empty()

template<typename T>

bool mtcore::Optional< T >::empty ( ) const

inlinenodiscardnoexcept

Returns

if is empty

Definition at line 299 of file optional.hpp.

{ return std::holds_alternative<std::monostate>(v); }

has_value()

template<typename T>

bool mtcore::Optional< T >::has_value ( ) const

inlinenodiscardnoexcept

Returns

if has a value

Definition at line 294 of file optional.hpp.

{ return std::holds_alternative<T>(v); }

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move_if_present()

template<typename T>

bool mtcore::Optional< T >::move_if_present ( T & out )

inlinenodiscardnoexcept

Moves a value to a reference output destination if a value is present.

Will mark the Optional as empty Designed to be used by simple iterators as part of a while loop on a next() method Example:

auto iter = myCollection.iter();
T myVal;
while (iter.next().move_if_present(myVal)) {
   // loop contents
}

Parameters

out	Where to put the destination

Returns

true if a value was copied, false otherwise

Definition at line 352 of file optional.hpp.

                                                        {
      if (has_value()) {
        out = std::move(std::get<T>(v));
        v   = std::monostate{};
        return true;
      }
      return false;
    }

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operator*() [1/2]

template<typename T>

T & mtcore::Optional< T >::operator* ( )

inline

Dereferences the internal value.

Definition at line 380 of file optional.hpp.

                   {
      ensure(has_value(), "CANNNOT DERERFERENCE NULL OPTIONAL");
      return std::get<T>(v);
    }

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operator*() [2/2]

template<typename T>

const T & mtcore::Optional< T >::operator* ( ) const

inline

Dereferences the internal value.

Definition at line 364 of file optional.hpp.

                               {
      ensure(has_value(), "CANNNOT DERERFERENCE NULL OPTIONAL");
      return std::get<T>(v);
    }

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operator->() [1/2]

template<typename T>

T * mtcore::Optional< T >::operator-> ( )

inline

Dereferences the internal value.

Definition at line 388 of file optional.hpp.

                    {
      ensure(has_value(), "CANNNOT DERERFERENCE NULL OPTIONAL");
      return &std::get<T>(v);
    }

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operator->() [2/2]

template<typename T>

const T * mtcore::Optional< T >::operator-> ( ) const

inline

Dereferences the internal value.

Definition at line 372 of file optional.hpp.

                                {
      ensure(has_value(), "CANNNOT DERERFERENCE NULL OPTIONAL");
      return &std::get<T>(v);
    }

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operator==() [1/2]

template<typename T>

bool mtcore::Optional< T >::operator== ( const Optional< T > & other ) const

inlinenoexcept

Checks if value is equal to another Optional.

Definition at line 258 of file optional.hpp.

                                                          {
      if (has_value() != other.has_value()) {
        return false;
      }
      if (!has_value()) {
        return true;
      }
 
      ensure(has_value() && other.has_value(), "EXISTS CHECK FAILED");
      return std::get<T>(v) == std::get<T>(other.v);
    }

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operator==() [2/2]

template<typename T>

bool mtcore::Optional< T >::operator== ( const T & other ) const

inlinenoexcept

Checks if value is equal to a non-Optional value.

Definition at line 273 of file optional.hpp.

                                                   {
      if (!has_value()) {
        return false;
      }
      return std::get<T>(v) == other;
    }

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value() [1/2]

template<typename T>

const T & mtcore::Optional< T >::value ( ) const

inlinenodiscardnoexcept

Definition at line 306 of file optional.hpp.

                                                  {
      ensure(has_value(), "CANNOT GET VALUE WHEN OPTIONAL IS EMPTY");
      return std::get<T>(v);
    }

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value() [2/2]

template<typename T>

T & mtcore::Optional< T >::value ( )

inlinenodiscardnoexcept

Definition at line 301 of file optional.hpp.

                                      {
      ensure(has_value(), "CANNOT GET VALUE WHEN OPTIONAL IS EMPTY");
      return std::get<T>(v);
    }

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value_or()

template<typename T>

T mtcore::Optional< T >::value_or ( const T & def ) const

inlinenodiscardnoexcept

Returns the value in the optional, or a default value if the optional is empty.

Parameters

def	Default value

Definition at line 284 of file optional.hpp.

                                                          {
      if (has_value()) {
        return value();
      }
      return def;
    }

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

• optional.hpp