Re: Does D have class' attributes like C#'s?
On Saturday, 16 December 2017 at 19:57:30 UTC, Marc wrote: Does D have something similar? As others have said, D has UDAs. An alternative to using __traits(getAttributes) is to use std.traits.getUDAs [1] I've made a small example using std.traits.getUDAs, based off of your example. [2] [1] https://dlang.org/library/std/traits/get_ud_as.html [2] https://run.dlang.io/is/PTfEcw(I hope that link works)
Re: Does D have class' attributes like C#'s?
On 2017-12-16 22:11, Marc wrote:
I can't "pack" an object, right? In C#, TextSize is a class and 256 is
constructor's first argument. In D it's pretty much an array but I guess
it's close enough. Thanks!
In D it's an tuple of basically anything that is known at compile time,
values or types:
alias foo = int;
struct TextSize
{
int value;
}
int bar(int a) { return a; }
@(foo, 3, "asd", TextSize(256), bar(3))
class A {}
The following syntax is syntax sugar:
@TextSize(256)
class B {}
For:
@(TextSize(256))
class B {}
What's happening is that TextSize (all structs) has an implicit
construct for all fields. An instance of TextSize is constructed at
compile time and is used as a value in the UDA tuple.
The UDAs only exists during compile time (unless you explicitly save
them somehow). Runtime reflection cannot be used, but compile time
reflection can be used, using the "getAttribute" traits [1[
[1] https://dlang.org/spec/traits.html#getAttributes
--
/Jacob Carlborg
Re: Does D have class' attributes like C#'s?
On Saturday, 16 December 2017 at 21:11:43 UTC, Marc wrote:
On Saturday, 16 December 2017 at 20:05:15 UTC, Anonymouse wrote:
On Saturday, 16 December 2017 at 19:57:30 UTC, Marc wrote:
C# has a quite nice way to store metadata about a property by
a feature called atributes[1]. For example, I can write
something like this:
class A {
[TextSize(256)]
string Name { get; set; }
}
So using runtime/reflection I can retrieve the TextSize value
associated to A.name property.
Does D have something similar?
UDAs? User Defined Attributes.
https://dlang.org/spec/attribute.html#UserDefinedAttribute
http://ddili.org/ders/d.en/uda.html
class A {
@TextSize(256)
string name() { /* ... */ }
}
I can't "pack" an object, right? In C#, TextSize is a class and
256 is constructor's first argument. In D it's pretty much an
array but I guess it's close enough. Thanks!
No, it's either a struct or a class and it's not included in the
class itself.
You use the __trait(getAttributes) to retrieve the value when
needed:
```
struct TextSize {int value;}
class A {
@TextSize(256)
string name() { return ""; }
}
class B {
string name() { return ""; }
}
static assert(__traits(classInstanceSize, A) ==
__traits(classInstanceSize, B));
```
Re: Does D have class' attributes like C#'s?
On Saturday, December 16, 2017 21:11:43 Marc via Digitalmars-d-learn wrote:
> On Saturday, 16 December 2017 at 20:05:15 UTC, Anonymouse wrote:
> > On Saturday, 16 December 2017 at 19:57:30 UTC, Marc wrote:
> >> C# has a quite nice way to store metadata about a property by
> >> a feature called atributes[1]. For example, I can write
> >>
> >> something like this:
> >>> class A {
> >>>
> >>>[TextSize(256)]
> >>>string Name { get; set; }
> >>>
> >>> }
> >>
> >> So using runtime/reflection I can retrieve the TextSize value
> >> associated to A.name property.
> >>
> >> Does D have something similar?
> >
> > UDAs? User Defined Attributes.
> >
> > https://dlang.org/spec/attribute.html#UserDefinedAttribute
> > http://ddili.org/ders/d.en/uda.html
> >
> > class A {
> >
> > @TextSize(256)
> > string name() { /* ... */ }
> >
> > }
>
> I can't "pack" an object, right? In C#, TextSize is a class and
> 256 is constructor's first argument. In D it's pretty much an
> array but I guess it's close enough. Thanks!
What do you mean by pack? You can mess with the alignment of a struct to
reduce how much space it takes up if that's what you're talking about:
https://dlang.org/spec/struct.html
http://ddili.org/ders/d.en/memory.html
But you can't do that with classes. The compiler controls their layout and
can muck with it if it thinks that that makes it more efficient or whatnot,
whereas structs have the layout you tell them so that they can match up with
C structs as well as be used for managing how things are laid out in memory.
As for string being "pretty much an array," it's exactly an array. string is
just an alias for immutable(string)[], and underneath the hood, dynamic
arrays are essentially
struct DynamicArray(T)
{
size_t length;
T* ptr;
}
- Jonathan M Davis
Re: Does D have class' attributes like C#'s?
On Saturday, 16 December 2017 at 20:05:15 UTC, Anonymouse wrote:
On Saturday, 16 December 2017 at 19:57:30 UTC, Marc wrote:
C# has a quite nice way to store metadata about a property by
a feature called atributes[1]. For example, I can write
something like this:
class A {
[TextSize(256)]
string Name { get; set; }
}
So using runtime/reflection I can retrieve the TextSize value
associated to A.name property.
Does D have something similar?
UDAs? User Defined Attributes.
https://dlang.org/spec/attribute.html#UserDefinedAttribute
http://ddili.org/ders/d.en/uda.html
class A {
@TextSize(256)
string name() { /* ... */ }
}
I can't "pack" an object, right? In C#, TextSize is a class and
256 is constructor's first argument. In D it's pretty much an
array but I guess it's close enough. Thanks!
Re: Does D have class' attributes like C#'s?
On Saturday, 16 December 2017 at 19:57:30 UTC, Marc wrote:
C# has a quite nice way to store metadata about a property by a
feature called atributes[1]. For example, I can write something
like this:
class A {
[TextSize(256)]
string Name { get; set; }
}
So using runtime/reflection I can retrieve the TextSize value
associated to A.name property.
Does D have something similar?
UDAs? User Defined Attributes.
https://dlang.org/spec/attribute.html#UserDefinedAttribute
http://ddili.org/ders/d.en/uda.html
class A {
@TextSize(256)
string name() { /* ... */ }
}
Does D have class' attributes like C#'s?
C# has a quite nice way to store metadata about a property by a
feature called atributes[1]. For example, I can write something
like this:
class A {
[TextSize(256)]
string Name { get; set; }
}
So using runtime/reflection I can retrieve the TextSize value
associated to A.name property.
Does D have something similar?
