Trait sqlx::Decode [−][src]
pub trait Decode<'r, DB> where
DB: Database, { fn decode(
value: <DB as HasValueRef<'r>>::ValueRef
) -> Result<Self, Box<dyn Error + Sync + Send + 'static, Global>>; }
Expand description
A type that can be decoded from the database.
How can I implement Decode
?
A manual implementation of Decode
can be useful when adding support for
types externally to SQLx.
The following showcases how to implement Decode
to be generic over Database
. The
implementation can be marginally simpler if you remove the DB
type parameter and explicitly
use the concrete ValueRef
and TypeInfo
types.
struct MyType; // DB is the database driver // `'r` is the lifetime of the `Row` being decoded impl<'r, DB: Database> Decode<'r, DB> for MyType where // we want to delegate some of the work to string decoding so let's make sure strings // are supported by the database &'r str: Decode<'r, DB> { fn decode( value: <DB as HasValueRef<'r>>::ValueRef, ) -> Result<MyType, Box<dyn Error + 'static + Send + Sync>> { // the interface of ValueRef is largely unstable at the moment // so this is not directly implementable // however, you can delegate to a type that matches the format of the type you want // to decode (such as a UTF-8 string) let value = <&str as Decode<DB>>::decode(value)?; // now you can parse this into your type (assuming there is a `FromStr`) Ok(value.parse()?) } }