Trait diesel::prelude::OptionalExtension
source · pub trait OptionalExtension<T> {
// Required method
fn optional(self) -> Result<Option<T>, Error>;
}
Expand description
See the method documentation.
Required Methods§
sourcefn optional(self) -> Result<Option<T>, Error>
fn optional(self) -> Result<Option<T>, Error>
Converts a QueryResult<T>
into a QueryResult<Option<T>>
.
By default, Diesel treats 0 rows being returned from a query that is expected to return 1
row as an error (e.g. the return value of get_result
or first
). This method will
handle that error, and give you back an Option<T>
instead.
§Example
use diesel::{QueryResult, NotFound, OptionalExtension};
let result: QueryResult<i32> = Ok(1);
assert_eq!(Ok(Some(1)), result.optional());
let result: QueryResult<i32> = Err(NotFound);
assert_eq!(Ok(None), result.optional());