Express "Class argument may not be null" ?
ag0aep6g via Digitalmars-d-learn
digitalmars-d-learn at puremagic.com
Tue Aug 8 11:56:36 PDT 2017
On 08/08/2017 08:34 PM, Johan Engelen wrote:
> How would you express the function interface intent that a reference
> to a class may not be null?
> For a function "void foo(Klass)", calling "foo(null)" is valid. How do I
> express that that is invalid? (let's leave erroring with a compile error
> aside for now)
>
> Something equivalent to C++'s pass by reference: "void foo(Klass&)".
A contract might be the best you can do:
----
void foo(Klass k)
in { assert(k !is null); }
body {}
----
Or throw an exception.
> (note: I mean D classes, for structs "ref" works)
But you can pass null in a ref parameter:
----
void f(ref int x) @safe {}
void main() @safe
{
int* p = null;
f(*p);
}
----
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