class variable initialization

[Ali Çehreli]

On 4/15/23 09:06, NonNull wrote:

 >> struct Wrapper
 >> {
 >>    Object x = new Object();
 >>    alias x this;
 >> }

 > Amazing, was this always so?

At least for a long time. However, every Wrapper object will have a 
pointer to that single shared object.

If you think that cost is unnecessary, you can have a static variable:

struct Wrapper
{
    static Object x;
    alias x this;
}

static this() {
     Wrapper.x = new Object();
}

However, because such data are thread-local by-default, not the entire 
class, but each thread will have a copy that variable.

When you want a single class variable for all threads, then it must be 
defined as shared:

struct Wrapper
{
    shared static Object x;
    alias x this;
}

shared static this() {
     Wrapper.x = new Object();
}

void foo(shared Object o)
{
    assert(o !is null);
}

Note how foo's interface had to be changed as well. And of course you 
may have to provide thread synchronization when that variable needs to 
be mutated at run time.

Ali