Samples showing [out] interface params

[heaths]

Most usage of com I could find were using 0.2.0, but I after a lot of consideration and searching for samples, I realized you can simply use Option<T> for an interface instead of messing with *mut T for interfaces, making this considerably easier.

Having a sample and/or doc about this would be incredibly useful - perhaps a modification of the simple sample you have now. I was considering something like an offspring method that returns a COM enumerable which also shows how to allocate an array (for IEnumXXX::Next), but seems a bit involved for a sample.

[rylev]

@heaths I believe we have a sample like this already here. Does that cover what you're referring to? Perhaps we just need to make that doc more visible?

[DataTriny]

Hello @rylev,

The documentation you mentioned above seems outdated.

It lacks &self arguments on methods, and more importantly, if I do this:

com::interfaces! {
	#[uuid("...")]
	pub unsafe interface IMyInterface: IUnknown {
		pub fn get_other(
			&self,
			p_ret_val: &mut Option<IMyOtherInterface>
		) -> HRESULT;
	}
	
	#[uuid("...")]
	pub unsafe interface IMyOtherInterface: IUnknown {
		pub fn get_value(
			&self,
			p_ret_val: *mut u8
		) -> HRESULT;
	}
}

I get the following errors:

error: unexpected argument type: reference type
  --> src\com_interfaces.rs:11:15
   |
11 |             p_ret_val: &mut Option<IMyOtherInterface>
   |                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error[E0412]: cannot find type `IMyInterfaceVTable` in this scope
  --> src\com_interfaces.rs:6:1
   |
6  | / com::interfaces! {
7  | |     #[uuid("...")]
8  | |     pub unsafe interface IMyInterface: IUnknown {
9  | |         pub fn get_other(
...  |
25 | |     }
26 | | }
   | |_^ not found in this scope
   |

error[E0637]: `&` without an explicit lifetime name cannot be used here
  --> src\com_interfaces.rs:11:15
   |
11 |             p_ret_val: &mut Option<IMyOtherInterface>
   |                        ^ explicit lifetime name needed here

error[E0599]: no method named `get_abi` found for enum `com::Param<'_, &mut Option<IMyOtherInterface>>` in the current scope
  --> src\com_interfaces.rs:6:1
   |
6  | / com::interfaces! {
7  | |     #[uuid("...")]
8  | |     pub unsafe interface IMyInterface: IUnknown {
9  | |         pub fn get_other(
...  |
25 | |     }
26 | | }
   | |_^ method not found in `com::Param<'_, &mut Option<IMyOtherInterface>>`
   |
   = note: the method `get_abi` exists but the following trait bounds were not satisfied:
           `&mut Option<IMyOtherInterface>: AbiTransferable`
           `<&mut Option<IMyOtherInterface> as AbiTransferable>::Abi = _`
   = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)

[rylev]

@DataTriny whoops! This should be fixed in #183

[heaths]

Yes, that seems to cover it. So we don't need to declare *mut * mut T and cast? That's a load off the keyboard.

Maybe it's just because I'm still a Rust n00b, but might also be worth showing an example (and I'd be happy to contribute) with IEnumXXX interfaces, such that you can declare an [Option<IInterface>; 1] array (or larger) for Next.