Struct EntityId 

pub struct EntityId { /* private fields */ }

Identifies one database record: which table it lives in, plus its primary key within that table.

This is the type-erased counterpart to an Entity’s primary key. Equality and hashing cover both fields, so two entities of different types never collide even if their key bytes agree, and an id built from a borrowed key compares equal to one built from the owned form.

Invariant

Entity::TABLE_NAME has to identify the Rust type uniquely. This type only ever compares table names (Self::matches_type), while the operations which act on the entity behind an id recover the type by downcasting, so the two notions of identity have to agree. Were two entity types ever to share a table name, matches_type would answer true for both while the downcast succeeded for only one — turning the expects which pair the two into panics, and making bulk deletions silently match nothing. Adding an entity therefore means giving it a table name no other entity uses.

Implementations

impl EntityId

pub fn from_primary_key<E>(primary_key: E::PrimaryKey) -> Self

where E: Entity,

Build the id of the record of type E with this primary key.

The other constructors all funnel through here.

pub fn from_entity<E>(entity: &E) -> Self

where E: Entity,

Build the id of an entity instance.

Note that this asks the entity for its primary key, which for some entities means hashing their contents. Where the id is already available — as a cache key, say — reuse it rather than deriving it again.

pub fn from_borrowed_primary_key<E>(primary_key: &E::BorrowedPrimaryKey) -> Self

where E: Entity + BorrowPrimaryKey,

Build the id of the record of type E with this primary key, in its borrowed form.

Equal to what Self::from_primary_key produces for the owned form of the same key, so the two are interchangeable for lookups.

Trait Implementations

impl Clone for EntityId

fn clone(&self) -> EntityId

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for EntityId

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Display for EntityId

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Eq for EntityId

impl Hash for EntityId

fn hash<H: Hasher>(&self, state: &mut H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl PartialEq for EntityId

fn eq(&self, other: &Self) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.