Trait diesel::prelude::QueryableByName
source · pub trait QueryableByName<DB>where
Self: Sized,
DB: Backend,{
fn build<'a>(row: &impl NamedRow<'a, DB>) -> Result<Self>;
}Expand description
Deserializes the result of a query constructed with sql_query.
This trait can be derived
Examples
If we just want to map a query to our struct, we can use derive.
#[derive(QueryableByName, PartialEq, Debug)]
#[diesel(table_name = users)]
struct User {
id: i32,
name: String,
}
let first_user = sql_query("SELECT * FROM users ORDER BY id LIMIT 1")
.get_result(connection)?;
let expected = User { id: 1, name: "Sean".into() };
assert_eq!(expected, first_user);If we want to do additional work during deserialization, we can use
deserialize_as to use a different implementation.
struct LowercaseString(String);
impl Into<String> for LowercaseString {
fn into(self) -> String {
self.0
}
}
impl<DB, ST> FromSql<ST, DB> for LowercaseString
where
DB: Backend,
String: FromSql<ST, DB>,
{
fn from_sql(bytes: backend::RawValue<DB>) -> deserialize::Result<Self> {
String::from_sql(bytes)
.map(|s| LowercaseString(s.to_lowercase()))
}
}
#[derive(QueryableByName, PartialEq, Debug)]
#[diesel(table_name = users)]
struct User {
id: i32,
#[diesel(deserialize_as = LowercaseString)]
name: String,
}
let first_user = sql_query("SELECT * FROM users ORDER BY id LIMIT 1")
.get_result(connection)?;
let expected = User { id: 1, name: "sean".into() };
assert_eq!(expected, first_user);