UniqueResource, a C++ template class as a universal resource manager

[WhoCares]

Yes. I have done that for Windows native RPC handles.

The problem is, we have to specify the custom deleter each time when we declare a new variable. It's tedious. Maybe a typedef or "using"?
And, std::unique_ptr lacks abstraction for a default_value.

Also, we can add custom conversion operator for UniqueResource to avoid explicitly using
Get() method each time, just like "operator LPCSTR()", and "operator LPCWSTR()" of the ancient CString class from Microsoft.

    explicit operator ResourceType() const noexcept
    {
        return resource_;
    }

"explicit" can be omitted if you prefer convenience to safety.

samples of custom deleters for windows native RPC( "pointer" is defined for each functor):

struct StringBindingDeleter {
  typedef RPC_WSTR pointer;
  void operator()(RPC_WSTR stringBinding) {
    [[maybe_unused]] RPC_STATUS status = RpcStringFree(&stringBinding);
    assert(status == RPC_S_OK);
  }
};

struct RpcBindingDeleter {
  typedef RPC_BINDING_HANDLE pointer;
  void operator()(RPC_BINDING_HANDLE h) {
    [[maybe_unused]] RPC_STATUS status = RpcBindingFree(&h);
    assert(status == RPC_S_OK);
  }
};

usage:

  RPC_WSTR stringBinding = nullptr;
  status = RpcStringBindingCompose(nullptr, (RPC_WSTR)L"ncalrpc", nullptr,
                                   (RPC_WSTR)L"9038a9dd-b0f3-4745-827e-d4109e662cea", nullptr,
                                   (RPC_WSTR *)&stringBinding);
  if (status != RPC_S_OK || !stringBinding)
    return E_FAIL;

  std::unique_ptr stringBindingOwner(stringBinding, StringBindingDeleter);

  RPC_BINDING_HANDLE rpcBinding = nullptr;
  status = RpcBindingFromStringBinding(stringBinding, &rpcBinding);
  if (status != RPC_S_OK)
    return E_FAIL;

  std::unique_ptr rpcBindingOwner(rpcBinding, RpcBindingDeleter);

Originally Posted by atom0s

You can also do something similar to this by using the built-in 'std::shared_ptr' type. It allows for initialization with a custom deleter function. With that, you can pass a type cleanup call for types that have one. (You can also just define your own callback to cleanup custom/more unique types as needed.)

For example, using a 'HANDLE' type, which is cleaned up using 'CloseHandle':

const std::shared_ptr handle(::OpenProcess(PROCESS_VM_READ, FALSE, pid), ::CloseHandle);

Usage is then similar to your setup by just using 'handle.get()' to obtain the actual handle.