The following code snippet,

class DynamicIntegerArray $\{$

public:

DynamicIntegerArray$()$;

~DynamicIntegerArray$()$;

private:

unsigned int capacity $=4$;

unsigned int size $=0$;

int$*$ array $=$ nullptr;

$\}$;

DynamicIntegerArray::DynamicIntegerArray$()\{$

array $=$ new int$[$capacity$]$;

$\}$

DynamicIntegerArray::~DynamicIntegerArray$()\{$

delete$[]$ array;

$\}$

illustrates what programming idiom?

Copy and swap

Pointer To Implementation $($pImpl$)$

Resource Acquisition is Initialization $($RAII$)$

Substitution failure is not an error $($SFINAE$)$