C++ Insights

Source:

#include <type_traits>
#include <iostream>
#include <string>

template< typename TInstance, typename... TArguments >
inline auto StoreResource( TInstance* storage, TArguments&&... arguments )
	-> std::enable_if_t<std::is_move_assignable_v<TInstance> || std::is_copy_assignable_v<TInstance>>
{
	*storage = TInstance{ std::forward<TArguments>( arguments )... };
}

template< typename TInstance, typename... TArguments >
inline auto StoreResource( TInstance* storage, TArguments&&... arguments )
	-> std::enable_if_t<!std::is_move_assignable_v<TInstance> && !std::is_copy_assignable_v<TInstance>>
{
	storage->~TInstance();
	storage = new( storage ) TInstance{ std::forward<TArguments>( arguments )... };
}

struct Foo final
{
	float a;
	float b;
};

struct Bar final
{
	float a;
	float b;

Bar()					= default;
	Bar( const Bar& other )	: a{ other.a }, b{ other.b } {};
	Bar( Bar&& )			= delete;

Bar( float a, float b ) : a{ a }, b{ b } {};

inline Bar& operator = ( const Bar& other )
	{ 
		a = other.a;
		b = other.b;
		return *this;
	}
};

struct Jiz final
{
	float a;
	float b;

Jiz()				= default;
	Jiz( const Jiz& )	= delete;
	Jiz( Jiz&& )		= delete;
	
	Jiz( float a, float b ) : a{ a }, b{ b } {};
};

int main()
{
	Foo foo1;
	Bar bar1;
	Jiz jiz1;

StoreResource( &foo1, 3.14f, 7.83f );

std::cout << foo1.a << ' ' << foo1.b << std::endl;

StoreResource( &bar1, 3.15f, 7.84f );

std::cout << bar1.a << ' ' << bar1.b << std::endl;

StoreResource( &jiz1, 3.25f, 7.94f );

std::cout << jiz1.a << ' ' << jiz1.b << std::endl;
	
	return 0;
}

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