Am 13.07.2013 18:41, schrieb bearophile:
Benjamin Thaut:
I also wanted to mention the "ListAvailableCtors" template which is a
nice addition in case there is no constructor available to be called
with the given arguments. It will generate a list of all aviable ctors
with the types of its arguments, and thus greatly improve the error
message given when no appropriate constructor can be found:
string ListAvailableCtors(T)()
{
string result = "";
foreach(t; __traits(getOverloads, T, "__ctor"))
result ~= typeof(t).stringof ~ "\n";
return result;
}
In my original code it was used during construction like this:
static if(is(typeof(result.__ctor(args))))
{
result.__ctor(args);
}
else
{
static assert(args.length == 0 && !is(typeof(T.__ctor)), "Don't know
how to initialize an object of type " ~ T.stringof ~ " with
arguments:\n" ~ ARGS.stringof ~ "\nAvailable ctors:\n" ~
ListAvailableCtors!T() );
}
In my version of your code I have just added a template constraint, this
is simpler, and it generates an error at the calling point:
this(Targs...)(Targs args)
if (__traits(compiles, _instance.__ctor(args))) {
classInstanceBuf[] = typeid(T).init[];
_instance.__ctor(args);
}
Isn't this enough?
Bye,
bearophile
The problem with your version is that you will get something like:
Can't call ComposedClass.this with arguments (int, int, float)
With my version you will get:
Can't initialize object of type 'Foo' with arguments (int, int, float)
available ctors:
(int, int, int)
(int)
(float)
With my version you will instantly know what ctors are available and you
don't have to go look it up in the sourcecode.
Kind Regards
Benjamin Thaut
