my code

#include "DoublyLinkedList.h$"$

#include "DoublyLinkedListIterator.h$"$

#include

#include

#include

template

class List

$\{$

private:

using Node $=$ typename DoublyLinkedList::Node;

Node fHead;

Node fTail;

size$\_$t fSize;

public:

using Iterator $=$ DoublyLinkedListIterator;

List$()$ noexcept

: fHead$($nullptr$),$ fTail$($nullptr$),$ fSize$(0)\{\}$

List$($const List& aOther$)$

: fHead$($nullptr$),$ fTail$($nullptr$),$ fSize$(0)$

$\{$

for $($auto current $=$ aOther.fHead; current $!=$ nullptr; current $=$ current$->$fNext$)$

$\{$

push$\_$back$($current$->$fData$)$;

$\}$

$\}$

List& operator$=($const List& aOther$)$

$\{$

if $($this $!=$ &aOther$)$

$\{$

List temp$($aOther$)$;

swap$($temp$)$;

$\}$

return $*$this;

$\}$

List$($List&& aOther$)$ noexcept

: fHead$($aOther$.$fHead$),$ fTail$($aOther$.$fTail$),$ fSize$($aOther$.$fSize$)$

$\{$

aOther.fHead $=$ nullptr;

aOther.fTail $=$ nullptr;

aOther.fSize $=0$;

$\}$

List& operator$=($List&& aOther$)$ noexcept

$\{$

if $($this $!=$ &aOther$)$

$\{$

deleteAll$()$;

fHead $=$ aOther.fHead;

fTail $=$ aOther.fTail;

fSize $=$ aOther.fSize;

aOther.fHead $=$ nullptr;

aOther.fTail $=$ nullptr;

aOther.fSize $=0$;

$\}$

return $*$this;

$\}$

void swap$($List& aOther$)$ noexcept

$\{$

std::swap$($fHead$,$ aOther.fHead$)$;

std::swap$($fTail$,$ aOther.fTail$)$;

std::swap$($fSize$,$ aOther.fSize$)$;

$\}$

~List$()$

$\{$

deleteAll$()$;

$\}$

size$\_$t size$()$ const noexcept

$\{$

return fSize;

$\}$

template

void push$\_$front$($U&& aData$)$

$\{$

auto newNode $=$ DoublyLinkedList::makeNode$($std::forward$($aData$))$;

if $(!$fHead$)$

$\{$

fHead $=$ fTail $=$ newNode;

$\}$

else

$\{$

newNode$->$fNext $=$ fHead;

fHead$->$fPrevious $=$ newNode;

fHead $=$ newNode;

$\}$

$++$fSize;

$\}$

template

void push$\_$back$($U&& aData$)$

$\{$

auto newNode $=$ DoublyLinkedList::makeNode$($std::forward$($aData$))$;

if $(!$fTail$)$

$\{$

fHead $=$ fTail $=$ newNode;

$\}$

else

$\{$

newNode$->$fPrevious $=$ fTail;

fTail$->$fNext $=$ newNode;

fTail $=$ newNode;

$\}$

$++$fSize;

$\}$

void remove$($const T& aElement$)$ noexcept

$\{$

for $($auto current $=$ fHead; current $!=$ nullptr; current $=$ current$->$fNext$)$

$\{$

if $($current$->$fData $==$ aElement$)$

$\{$

if $($auto prev $=$ current$->$fPrevious.lock$())$

prev$->$fNext $=$ current$->$fNext;

else

fHead $=$ current$->$fNext;

if $($current$->$fNext$)$

current$->$fNext$->$fPrevious $=$ current$->$fPrevious;

else

fTail $=$ current$->$fPrevious.lock$()$;

current$->$isolate$()$;

$--$fSize;

return;

$\}$

$\}$

$\}$

const T& operator$[]($size$\_$t aIndex$)$ const

$\{$

if $($aIndex $>=$ fSize$)$

throw std::out$\_$of$\_$range$("$Index out of bounds"$)$;

auto current $=$ fHead;

for $($size$\_$t i $=0$; i $<$ aIndex; $++$i$)$

$\{$

current $=$ current$->$fNext;

$\}$

return current$->$fData;

$\}$

Iterator begin$()$ const noexcept

$\{$

return Iterator$($fHead$,$ fTail$)$;

$\}$

Iterator end$()$ const noexcept

$\{$

return Iterator$($nullptr$,$ nullptr$)$;

$\}$

Iterator rbegin$()$ const noexcept

$\{$

return Iterator$($fTail$,$ fHead$)$;

$\}$

Iterator rend$()$ const noexcept

$\{$

return Iterator$($nullptr$,$ nullptr$)$;

$\}$

private:

void deleteAll$()$

$\{$

while $($fHead$)$

$\{$

auto next $=$ fHead$->$fNext;

fHead$->$isolate$()$;

fHead $=$ next;

$\}$

fTail $=$ nullptr;

fSize $=0$;

$\}$

$\}$;

the error im getting

Exception thrown: read access violation.

$**$this$**$ was nullptr.

at this code in the xstring file

$))$