use super::*;
/// Wrapper for handling potentially NULL values.
/// ```
/// use extendr_api::prelude::*;
/// test! {
/// use extendr_api::wrapper::Nullable::*;
///
/// // Plain integer.
/// let s1 = r!(1);
/// let n1 = <Nullable<i32>>::from_robj(&s1)?;
/// assert_eq!(n1, NotNull(1));
///
/// // NA integer - error.
/// let sna = r!(NA_INTEGER);
/// assert_eq!(<Nullable<i32>>::from_robj(&sna).is_err(), true);
///
/// // NA integer - option gives none.
/// assert_eq!(<Nullable<Option<i32>>>::from_robj(&sna)?, NotNull(None));
///
/// // NULL object.
/// let snull = r!(NULL);
/// let nnull = <Nullable<i32>>::from_robj(&snull)?;
/// assert_eq!(nnull, Null);
///
/// assert_eq!(r!(Nullable::<i32>::Null), r!(NULL));
/// assert_eq!(r!(Nullable::<i32>::NotNull(1)), r!(1));
/// }
/// ```
#[derive(Debug, PartialEq, Clone)]
pub enum Nullable<T> {
NotNull(T),
Null,
}
impl<'a, T> FromRobj<'a> for Nullable<T>
where
T: FromRobj<'a>,
{
/// Convert an object that may be null to a rust type.
/// ```
/// use extendr_api::prelude::*;
/// test! {
/// let s1 = r!(1);
/// let n1 = <Nullable<i32>>::from_robj(&s1)?;
/// assert_eq!(n1, Nullable::NotNull(1));
/// let snull = r!(NULL);
/// let nnull = <Nullable<i32>>::from_robj(&snull)?;
/// assert_eq!(nnull, Nullable::Null);
/// }
/// ```
fn from_robj(robj: &'a Robj) -> std::result::Result<Self, &'static str> {
if robj.is_null() {
Ok(Nullable::Null)
} else {
Ok(Nullable::NotNull(<T>::from_robj(robj)?))
}
}
}
impl<T> From<Nullable<T>> for Robj
where
T: Into<Robj>,
{
/// Convert a rust object to NULL or another type.
/// ```
/// use extendr_api::prelude::*;
/// test! {
/// assert_eq!(r!(Nullable::<i32>::Null), r!(NULL));
/// assert_eq!(r!(Nullable::<i32>::NotNull(1)), r!(1));
/// }
/// ```
fn from(val: Nullable<T>) -> Self {
match val {
Nullable::NotNull(t) => t.into(),
Nullable::Null => r!(NULL),
}
}
}