Types: Nullable Types
A type ?Foo is either a value of type Foo, or null.
function takes_nullable_str(?string $s): string {
if ($s is null){
return "default";
} else {
return $s;
}
}
nonnull is any value except null. You can use it to check if a
value is not null:
function takes_nullable_str2(?string $s): string {
if ($s is nonnull){
return $s;
} else {
return "default";
}
}
This is slightly better than writing $s is string, as you don't need
to repeat the type name.
nonnull is also useful when using generics.
function my_filter_nulls<T as nonnull>(vec<?T> $items): vec<T> {
$result = vec[];
foreach ($items as $item) {
if ($item is null) {
// Discard it.
} else {
$result[] = $item;
}
}
return $result;
}
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