Struct HasOne 

pub struct HasOne<P, C>(/* private fields */);

One parent, one child.

The same query as HasMany; the difference is that you read it with Related::one. A second matching row is not an error here, because the database is where uniqueness belongs: put a unique index on the foreign key and the question cannot arise.

Implementations

impl<P: Model, C: Model> HasOne<P, C>

pub fn new() -> Self

With the conventional keys.

pub fn foreign_key(self, column: impl Into<String>) -> Self

The column on the child pointing back at the parent.

pub fn local_key(self, column: impl Into<String>) -> Self

The column on the parent the child points at.

pub fn matching(self, criteria: Criteria) -> Self

Narrow or order the children.

Trait Implementations

impl<P: Model, C: Model> Default for HasOne<P, C>

fn default() -> Self

Returns the “default value” for a type.

impl<P: Model, C: Model> Relation<P> for HasOne<P, C>

type Related = C

The model on the other side.

fn near_key(&self) -> &str

The column on P that identifies it in this relationship.

fn far_key(&self) -> &str

The column on the other side that this relationship matches against.

fn load<'life0, 'life1, 'life2, 'async_trait>( &'life0 self, parents: &'life1 [P], related: &'life2 dyn Repository<C>, ) -> Pin<Box<dyn Future<Output = Result<Related<C>>> + Send + 'async_trait>>

where Self: 'async_trait, 'life0: 'async_trait, 'life1: 'async_trait, 'life2: 'async_trait,

Load the related rows for every parent, in one query.

fn count<'life0, 'life1, 'life2, 'async_trait>( &'life0 self, parents: &'life1 [P], related: &'life2 dyn Repository<C>, ) -> Pin<Box<dyn Future<Output = Result<RelatedCounts>> + Send + 'async_trait>>

where Self: 'async_trait, 'life0: 'async_trait, 'life1: 'async_trait, 'life2: 'async_trait,

Count the related rows for every parent, in one query, without transferring them.

fn for_one<'life0, 'life1, 'life2, 'async_trait>( &'life0 self, parent: &'life1 P, related: &'life2 dyn Repository<Self::Related>, ) -> Pin<Box<dyn Future<Output = Result<Vec<Self::Related>>> + Send + 'async_trait>>

where Self: Sized + 'async_trait, 'life0: 'async_trait, 'life1: 'async_trait, 'life2: 'async_trait,

Load for a single parent.