Re: Restrict type of function parameter to a defined list of types?
On Sunday, 12 December 2021 at 14:26:54 UTC, Martin B wrote: On Sunday, 12 December 2021 at 14:11:48 UTC, Paul Backus wrote: You can use a [template constraint][1]: Hi Paul, yes! thats it, Thanks. I am facepalming me right now because have been on that webpage and missed that point. Happens to everyone at some time
Re: Restrict type of function parameter to a defined list of types?
On Sunday, 12 December 2021 at 14:11:48 UTC, Paul Backus wrote: You can use a [template constraint][1]: Hi Paul, yes! thats it, Thanks. I am facepalming me right now because have been on that webpage and missed that point.
Re: Restrict type of function parameter to a defined list of types?
On Sunday, 12 December 2021 at 13:42:08 UTC, Martin B wrote:
On Sunday, 12 December 2021 at 13:21:06 UTC, Adam D Ruppe wrote:
On Sunday, 12 December 2021 at 13:11:58 UTC, Martin B wrote:
Just add a forwarding overload:
Hi Adam,
i am wondering if there is another possibility without having
to create overloads for each parameter type - something like
this pseudocode:
```
Nullable!string str(T : {string, Nullable!string}) (T setter) {
return this._str = setter;
}
```
You can use a [template constraint][1]:
```d
Nullable!string str(T)(T setter)
if (is(T == string) || is(T == Nullable!string))
{
return this._str = setter;
}
```
[1]: https://dlang.org/spec/template.html#template_constraints
Re: Restrict type of function parameter to a defined list of types?
On Sunday, 12 December 2021 at 13:21:06 UTC, Adam D Ruppe wrote:
On Sunday, 12 December 2021 at 13:11:58 UTC, Martin B wrote:
Just add a forwarding overload:
Hi Adam,
i am wondering if there is another possibility without having to
create overloads for each parameter type - something like this
pseudocode:
```
Nullable!string str(T : {string, Nullable!string}) (T setter) {
return this._str = setter;
}
```
Re: Restrict type of function parameter to a defined list of types?
On Sunday, 12 December 2021 at 13:11:58 UTC, Martin B wrote:
Hi everyone,
lets say that required is a setter method:
```
Nullable!string str(Nullable!string setter) {
return this._str = setter;
}
```
Just add a forwarding overload:
auto str(string s) { return this.str(nullable(s)); }
Then the user can pass either Nullable or string but not other
things.
Restrict type of function parameter to a defined list of types?
Hi everyone,
lets say that required is a setter method:
```
Nullable!string str(Nullable!string setter) {
return this._str = setter;
}
```
The user should be able to:
```
auto a = new A();
a.str = "abc";
```
As the setters parameter is defined to be of type
`Nullable!string`, the compiler complains. So the user need to
do `a.str = nullable("abc");`
I guess a solution could be to define the setter as:
```
Nullable!string str(T)(T setter) {
return this._str = setter;
}
```
^stupid question: Is this the correct way to restrict the
parameter type to be `string` or `Nullable!string` or is there a
more precise way to restrict?
BTW: here is a more complete simple example of what i am talking
about: https://run.dlang.io/is/zP4vkb
