Re: Linker Error with Template Function
On Saturday, 1 October 2022 at 21:18:05 UTC, Ali Çehreli wrote: On 10/1/22 11:15, Kyle Ingraham wrote: > storing structs as > `void*` in a wrapper struct with information about their module and > identifier saved elsewhere. Perhaps unrelated but that part reminded me of the following discussion: https://forum.dlang.org/post/tfbn10$19nv$1...@digitalmars.com Ali Thanks for this Ali. I found it useful to see another way to solve this problem. Seems like it would be great to have a `Type` type that can store a type at compile-time for use at run-time.
Re: Linker Error with Template Function
On 10/1/22 11:15, Kyle Ingraham wrote: > storing structs as > `void*` in a wrapper struct with information about their module and > identifier saved elsewhere. Perhaps unrelated but that part reminded me of the following discussion: https://forum.dlang.org/post/tfbn10$19nv$1...@digitalmars.com Ali
Re: Linker Error with Template Function
On Tuesday, 13 September 2022 at 08:43:45 UTC, Nick Treleaven
wrote:
On Tuesday, 13 September 2022 at 03:00:17 UTC, Kyle Ingraham
wrote:
Any suggestions for being able to call one function for any
instance given but maintain flexible return types?
Not sure if it helps, but you can define final methods in an
interface, which can call virtual interface methods:
```d
interface PathConverter
{
string getValue();
final T toD(T)()
{
import std.conv : to;
return to!T(getValue());
}
}
```
Not tested as AFK.
Thanks for the suggestion Nick. I solved this by storing structs
as `void*` in a wrapper struct with information about their
module and identifier saved elsewhere. I use that information to
setup casts to the appropriate type then call `toD`. That way I
can call the same method for functions that return different
types and store disparate structs to the same wrapper struct. The
wrapper struct gets used in function signatures.
Re: Linker Error with Template Function
On Tuesday, 13 September 2022 at 03:00:17 UTC, Kyle Ingraham
wrote:
Any suggestions for being able to call one function for any
instance given but maintain flexible return types?
Not sure if it helps, but you can define final methods in an
interface, which can call virtual interface methods:
```d
interface PathConverter
{
string getValue();
final T toD(T)()
{
import std.conv : to;
return to!T(getValue());
}
}
```
Not tested as AFK.
Re: Linker Error with Template Function
On Tuesday, 13 September 2022 at 01:46:14 UTC, Paul Backus wrote:
On Tuesday, 13 September 2022 at 00:57:58 UTC, Kyle Ingraham
wrote:
I am writing a library where I would like to be able to store
instances of a type of class to an associative array for later
usage. Each class stored has to implement a function as part
of the required interface. The argument given is always the
same type but the return value should be flexible. I solved
this with an interface:
```d
interface PathConverter
{
T toD(T)(const string value) @safe;
}
```
https://dlang.org/spec/template.html#limitations
Templates cannot be used to add non-static fields or virtual
functions to classes or interfaces.
You *should* get an error from the compiler for trying to do
this, instead of just a linker error somewhere else down the
line, but either way it's not going to work. You'll have to
find another solution.
Thanks for the spec help Paul. I must've skirted around the
compiler somehow. This is a minimal example that triggers the
linker error:
```d
interface PathConverter
{
T toD(T)(string value);
}
class NumberConverter(T) : PathConverter
{
T toD(T)(string value)
{
import std.conv : to;
return to!T(value);
}
}
alias IntConverter = NumberConverter!int;
void main()
{
PathConverter[string] allConverters;
allConverters["int"] = new IntConverter;
int converted = allConverters["int"].toD!int("9");
}
```
Any suggestions for being able to call one function for any
instance given but maintain flexible return types?
Re: Linker Error with Template Function
On Tuesday, 13 September 2022 at 00:57:58 UTC, Kyle Ingraham
wrote:
I am writing a library where I would like to be able to store
instances of a type of class to an associative array for later
usage. Each class stored has to implement a function as part of
the required interface. The argument given is always the same
type but the return value should be flexible. I solved this
with an interface:
```d
interface PathConverter
{
T toD(T)(const string value) @safe;
}
```
https://dlang.org/spec/template.html#limitations
Templates cannot be used to add non-static fields or virtual
functions to classes or interfaces.
You *should* get an error from the compiler for trying to do
this, instead of just a linker error somewhere else down the
line, but either way it's not going to work. You'll have to find
another solution.
