The Problem i found with the Template versions is, that you can t add the Singleton Template from another Module. So you have to have the Singleton Template in every Module you want to have a SingletonClass (I think)

That shouldn’t be happening. I’ve not been able to reproduce it myself. As long as you import the module that declares the singleton instance, you should be able to use it anywhere. It might break on Windows when compiled into a static library (a known template problem on that platform) but other than that it should work fine.

@Stephane:

can I have the same problem with a multithreaded environment ? about the Double-Checked Locking ?

The version that uses a static constructor should be thread-safe, as far as accessing the singleton instance is concerned. No need for any locking or other synchronization measures.

Thanks for this tutorial about the Singleton pattern, but can I have the same problem with a multithreaded environment ? about the Double-Checked Locking ?

bye

I made something with Mixins today:
template Singleton() {
public:
static typeof(this) getInstance() {
if (_instance is null) _instance = new typeof(this)();
return _instance;
};
private:
this() { writefln(“Singleton Constructor”); };
static typeof(this) _instance;
};

class ResourceLoader {
mixin Singleton!();

int some_more_stuff;

private:
this() { writefln(“ResourceLoader Constructor”); };
}

bye