D 2015/2016 Vision?

[Namespace via Digitalmars-d]

On Sunday, 4 October 2015 at 20:18:25 UTC, rsw0x wrote:
> On Sunday, 4 October 2015 at 18:02:21 UTC, bitwise wrote:
>> Currently, it seems like someone will eventually take all 
>> these classes/hierarchies and flatten them into some 
>> struct/template approach. I am not looking forward to this at 
>> all. I like polymorphism when it's appropriate.
>
> It's just a symptom of D classes being so difficult to use 
> without the GC, compared to when I first picked up D to now I 
> find myself barely *ever* using classes and just C-style(er, 
> D-style?) polymorphism with structs, mixins, and alias this.
> Bye.

You can use classes without GC _and_ with deteministic lifetime:

----
import std.stdio;

class A {
	string name;
	
	this(string name) {
		this.name = name;
	}
	
	void hello() {
		writeln("Hallo, ", this.name);
	}
}

struct Scoped(T) if (is(T == class)) {
	import core.stdc.stdlib : malloc, free;
	
	enum SIZE = __traits(classInstanceSize, T);
	
	T obj;
	
	this(Args...)(auto ref Args args) {
		void[] buffer = malloc(SIZE)[0 .. SIZE];
		buffer[] = typeid(T).init[];
		
		this.obj = cast(T) buffer.ptr;
		this.obj.__ctor(args);
	}
	
	~this() {
		destroy(this.obj);
		free(cast(void*) this.obj);
	}
	
	alias obj this;
}

auto scoped(T, Args...)(auto ref Args args) if (is(T == class)) {
	return Scoped!T(args);
}

void main() {
	auto a = scoped!A("Foo");
	a.hello();
}
----