On Tuesday, 26 May 2020 at 12:08:29 UTC, Johannes Loher wrote:
On Tuesday, 26 May 2020 at 11:44:58 UTC, Vinod K Chandran wrote:
On Monday, 25 May 2020 at 16:39:30 UTC, Mike Parker wrote:
On Monday, 25 May 2020 at 08:39:23 UTC, John Burton wrote:
I believe that in D *this* is a reference to the
object and not a pointer like in C++.
So I think that writing &this might be what you need?
No. A class reference is a pointer under the hood. Getting
its address will result in a pointer to the reference
variable itself, not to the class instance. When passing a
reference to a C API, casting it directly to the C type is
correct.
Try this code. This will reproduce the same error.
import std.stdio : log = writeln;
void main() {
log("Let's check whether 'this' is an lvalue or not.");
Button btn = new Button("A button");
}
class Button {
this(string btntext) {
mtext = btntext;
log("button created with the name , ", btntext);
log(&this);
}
private:
string mt
}
It doesn't compile, the line
string mt
should be
string mtext;
instead. Indeed, we get a compiler error:
Error: this is not an lvalue and cannot be modified.
The problem is in line 11: You are trying to get the address of
`this`. But `this` is an lvalue, so it does not have an address
you could take. It becomes mir clear that this doesn’t work if
you consider other lvalues, like literals:
int* = &1; // doesn’t compile, can’t take the address of an
lvalue.
In this code example, the correct thing to do is to simply not
take the address but pass `this` to `writeln`. That compiles
and results in the following output:
Let's check whether 'this' is an lvalue or not.
button created with the name , A button
onlineapp.Button
(The module is onlineapp because I ran it in run.dlang.io)
I don't know what the correct thing would be in your original
code though.
You can just do this to get around it:
auto button = this;
log(&button);
