Trait diesel::connection::Connection [−] [src]

pub trait Connection: SimpleConnection + Sized + Send {
    type Backend: Backend;
    fn establish(database_url: &str) -> ConnectionResult<Self>;

    fn transaction<T, E, F>(&self, f: F) -> Result<T, E>
    where
        F: FnOnce() -> Result<T, E>,
        E: From<Error>,
    { ... }
    fn begin_test_transaction(&self) -> QueryResult<()> { ... }
    fn test_transaction<T, E, F>(&self, f: F) -> T
    where
        F: FnOnce() -> Result<T, E>,
    { ... }
}

Perform connections to a backend.

Associated Types

The backend this connection represents.

Required Methods

Establishes a new connection to the database at the given URL. The URL should be a valid connection string for a given backend. See the documentation for the specific backend for specifics.

Provided Methods

Executes the given function inside of a database transaction. When a transaction is already occurring, savepoints will be used to emulate a nested transaction.

The error returned from the function must implement From<diesel::result::Error>.

Examples:

use diesel::result::Error;

fn main() {
    let conn = establish_connection();
    let _ = conn.transaction::<_, Error, _>(|| {
        let new_user = NewUser { name: "Ruby".into() };
        diesel::insert(&new_user).into(users::table).execute(&conn)?;
        assert_eq!(users::table.load::<User>(&conn), Ok(vec![
            User { id: 1, name: "Sean".into() },
            User { id: 2, name: "Tess".into() },
            User { id: 3, name: "Ruby".into() },
        ]));

        Ok(())
    });

    let _ = conn.transaction::<(), Error, _>(|| {
        let new_user = NewUser { name: "Pascal".into() };
        diesel::insert(&new_user).into(users::table).execute(&conn)?;

        assert_eq!(users::table.load::<User>(&conn), Ok(vec![
            User { id: 1, name: "Sean".into() },
            User { id: 2, name: "Tess".into() },
            User { id: 3, name: "Ruby".into() },
            User { id: 4, name: "Pascal".into() },
        ]));

        Err(Error::RollbackTransaction) // Oh noeees, something bad happened :(
    });

    assert_eq!(users::table.load::<User>(&conn), Ok(vec![
        User { id: 1, name: "Sean".into() },
        User { id: 2, name: "Tess".into() },
        User { id: 3, name: "Ruby".into() },
    ]));
}

Creates a transaction that will never be committed. This is useful for tests. Panics if called while inside of a transaction.

Executes the given function inside a transaction, but does not commit it. Panics if the given function returns an Err.

Implementors