On 22 May 2020, at 04:24, Sean P. DeNigris <sean@clipperadams.com> wrote:

Esteban Lorenzano wrote
The class comments are not clear?

Maybe it's me ;-)


Esteban Lorenzano wrote
Opaque object = https://en.wikipedia.org/wiki/Opaque_data_type
&lt;https://en.wikipedia.org/wiki/Opaque_data_type&gt;
External object = a pointer to something. 

For example, why is ObjCClass a subclass of FFIExternalObject instead of
FFIOpaqueObject when the docs say that a "Class [is] An opaque type that
represents an Objective-C class"? Also, is the distinction just conceptual?
I don't see what either class "buys" you in behavior since they are siblings
that both pretty much have no methods.

This is because ObjCClass = SomeOpaqueStructurePointer (is already a pointer), same as ObjCSelector and ObjCMethod.
Difference is subtle, because is just a different way of representing the same. 

The easiest way I have to explain is: 

You use an OpaqueObject when you will refer to the opaque type in calls as:  someFunction(opaqueobject *someArg).
You use an ExternalObject when you will refer to the opaque type in calls as: someFunction(externalobject someArg).

Esteban




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Cheers,
Sean
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