Trait mysql_async::prelude::FromRow
source · pub trait FromRow {
// Required method
fn from_row_opt(row: Row) -> Result<Self, FromRowError>
where Self: Sized;
// Provided method
fn from_row(row: Row) -> Self
where Self: Sized { ... }
}Expand description
Trait to convert Row into a tuple of FromValue implementors up to arity 12.
This trait is convenient way to convert mysql row to a tuple or rust types and relies on
FromValue trait, i.e. calling from_row::<(T, U)>(row) is similar to calling
(T::from_value(column_1), U::from_value(column_2)).
Note that conversion will always fail if any of columns was taken using Row::take method.
Conversion of individual columns of a row may fail. In this case from_row will panic, and
from_row_opt will roll back conversion and return original row.
Concrete types of columns in a row is usually known to a programmer so from_value should never
panic if types specified correctly. This means that column which holds NULL should correspond
to a type wrapped in Option, String is used only with column which hold correct utf8, size
and signedness of a numeric type should match to a value stored in a column and so on.
ⓘ
// Consider columns in the row is: Bytes(<some binary data>), NULL and Int(1024)
from_row::<(String, u8, u8)>(row) // this will panic because of invalid utf8 in first column.
from_row::<(Vec<u8>, u8, u8)>(row) // this will panic because of a NULL in second column.
from_row::<(Vec<u8>, Option<u8>, u8)>(row) // this will panic because 1024 does not fit in u8.
from_row::<(Vec<u8>)>(row) // this will panic because number of columns != arity of a tuple.
from_row::<(Vec<u8>, Option<u8>, u16, Option<u8>)>(row) // same reason of panic as previous.
from_row::<(Vec<u8>, Option<u8>, u16)>(row) // this'll work and return (vec![..], None, 1024u16)