On Saturday, 19 January 2019 at 14:26:31 UTC, Zenw wrote:
On Tuesday, 15 January 2019 at 11:14:54 UTC, John Burton wrote:
As an example let's say I have a type 'Window' that represents
a win32 window. I'd like to be able to construct an instance
of the type with some optional parameters that default to some
reasonable settings and create the underlying win32 window.
[...]
how about this
auto With(string code,T)(T value)
{
with(value)
{
mixin(code ~";");
}
return value;
}
auto window = Window().With!q{title = "My window",width =
800,fullscreen = true};
The problem with using string mixins like that is when you want
to use some local variable:
int width = getWidth();
auto window = Window().With!q{width = width};
This would work:
struct Window {
string title;
int width;
bool fullscreen;
}
auto With(T, Args...)(T ctx, Args args) {
static foreach (i; 0..Args.length) {
mixin("ctx."~Args[i].name~" = args[i].value;");
}
return ctx;
}
struct args {
static opDispatch(string _name, T)(T value) {
struct Result {
enum name = _name;
T value;
}
return Result(value);
}
}
unittest {
auto window = Window().With(args.title = "My window",
args.width = 800, args.fullscreen = true);
assert(window.title == "My window");
assert(window.width == 800);
assert(window.fullscreen == true);
}
However, I don't see that there's all that much gain compared to
just assigning the fields the normal way.
--
Simen
