• Antonio (2/2) Jun 20 2022 Is there any way to specify that a variable, member or parameter
• Dennis (8/10) Jun 20 2022 Depends on the type. Basic types can't be null. Pointers and
• max haughton (4/6) Jun 20 2022 You can use an invariant if it's a member of an aggregate but be
• Antonio (12/18) Jun 20 2022 I'm using preconditions when calling functions

Antonio <antonio abrevia.net> writes:

Is there any way to specify that a variable, member or parameter 
can't be null?

Dennis <dkorpel gmail.com> writes:

On Monday, 20 June 2022 at 17:48:48 UTC, Antonio wrote:
 Is there any way to specify that a variable, member or 
 parameter can't be null?

Depends on the type. Basic types can't be null. Pointers and 
classes can always be `null`, though you could wrap them in a 
custom library type that doesn't allow them to be `null`. Dynamic 
arrays and associative arrays can be null, but it's equivalent to 
them being empty, so you can still use them like normal. You can 
pass a struct as a `ref` parameter, which passes it by reference 
but it's still typed as a plain struct, so it can't be `null`.

max haughton <maxhaton gmail.com> writes:

On Monday, 20 June 2022 at 17:48:48 UTC, Antonio wrote:
 Is there any way to specify that a variable, member or 
 parameter can't be null?

You can use an invariant if it's a member of an aggregate but be 
warned that these are only checked at the boundaries of public 
member functions.

Antonio <antonio abrevia.net> writes:

On Monday, 20 June 2022 at 19:08:32 UTC, max haughton wrote:
 On Monday, 20 June 2022 at 17:48:48 UTC, Antonio wrote:
 Is there any way to specify that a variable, member or 
 parameter can't be null?

 You can use an invariant if it's a member of an aggregate but 
 be warned that these are only checked at the boundaries of 
 public member functions.

I'm using preconditions when calling functions

```d
auto readByCredentiasl(CredentialsDTO credentials)
in (credentials !is null)
in (credentias.username !is null)
...
{
  ...
}
```

But it's runtime validation, not formally validated by compiler.