article comparing Rust and Zig, many points relevant to D

[Adam D. Ruppe]

On Wednesday, 10 March 2021 at 21:51:43 UTC, mw wrote:
> What is the exact usage of this feature?

http://dpldocs.info/experimental-docs/source/arsd.jni.d.html#L1358

That _jmethodID is unique for each method added. So when you 
follow the example code:

http://dpldocs.info/experimental-docs/arsd.jni.html

and have like

	@Export void hi(string name) {
		import std.stdio;
		writefln("hello from D, %s", name);
         }

	// D can also access Java methods
	@Import void printMember();


Then hi and printMember both get their own private copy of the 
id. No conflict regardless of how many methods you mixin.

Notice too how these mixin static constructors too, which are all 
combined per language rules, allowing me to actually concatenate 
the lists at startup for a one-go load of metadata at runtime.

http://dpldocs.info/experimental-docs/source/arsd.jni.d.html#L1790


For the other side, adrdox uses that:

https://github.com/adamdruppe/adrdox/blob/master/doc2.d#L3169

That's a mixin template with semi-specialized implementations of 
the abstract interface.

But there's also cases like here:

https://github.com/adamdruppe/adrdox/blob/master/doc2.d#L3028

That override the mixed in override, letting you accept the 
default implementations in some places, and selectively override 
them for other methods, without having to create another child 
class to do it.


Now take a look at this line:
https://github.com/adamdruppe/adrdox/blob/master/doc2.d#L3158

Notice the explicit usage of `this` there. Without it, it would 
use the local name inside the mixin template and NOT respect the 
override; this is good when you want to use a private member like 
in the jni example. But with it, it looks up one level above 
which means the user can easily override it and then it respects 
this, similar to a virtual vs static lookup in oop (which itself 
can get a bit nuts if you use the curiously-recurring template 
pattern, which I do here for reflection of a child class inside 
the base class 
http://dpldocs.info/experimental-docs/source/arsd.cgi.d.html#L8288 - the mixin template version is kinda the same idea.)