Struct Relation 

pub struct Relation {
    pub model: String,
    pub field: String,
    pub kind: RelationKind,
    pub display_field: Option<String>,
    pub required: Option<bool>,
    pub on_delete: Option<String>,
}

First-class foreign-key annotation on a field.

Only belongs_to is stored explicitly. The inverse direction (has_many) is inferred at runtime by Schema::incoming_relations; adding it as a stored variant would double-book the same information and drift over time.

Conservative by design: if any of these fields is missing, old consumers ignore the whole relation key because the parent field is Option<Relation>.

0.9.0 write path

The primary writer is the #[rustio(belongs_to = "...")] macro attribute, which populates AdminRelation on the compiled model. Schema::from_admin copies that into SchemaField.relation so rustio.schema.json always matches the compiled types. Hand-edits to rustio.schema.json still work (the AI layer reads this shape), but the macro is authoritative: the next rustio schema overwrites any hand-added block without a matching macro attribute.

Fields

model: String

Target model name (e.g. "Patient").

field: String

Target field name — conventionally "id", but explicit so a future release can support multi-column keys without another schema bump.

kind: RelationKind

Direction marker. Stored writes only accept BelongsTo; HasMany is reserved for inferred inverse results.

display_field: Option<String>

0.9.0 — optional name of the target’s column whose value should be rendered as the human label for this foreign key in the admin. None means the admin will show #<id> rather than guess a column. No inference (full_name / name / title fallback) is ever applied — this is opt-in on purpose so that operators see raw IDs only when the model author has not declared a display field.

required: Option<bool>

0.9.0 — whether the FK column is NOT NULL. None is treated the same as Some(false) (nullable) — the Option lets 0.8.x schema files round-trip byte-identically when they don’t know about this key.

on_delete: Option<String>

0.9.0 — SQL ON DELETE policy. Stored as the serialised form ("restrict" / "cascade" / "set_null") so older tooling just sees a string. Missing → treat as restrict.

Trait Implementations

impl Clone for Relation

fn clone(&self) -> Relation

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for Relation

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

Formats the value using the given formatter.

impl<'de> Deserialize<'de> for Relation

fn deserialize<__D>(__deserializer: __D) -> Result<Self, __D::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl PartialEq for Relation

fn eq(&self, other: &Relation) -> 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.

impl Serialize for Relation

fn serialize<__S>(&self, __serializer: __S) -> Result<__S::Ok, __S::Error>

where __S: Serializer,

Serialize this value into the given Serde serializer.

impl StructuralPartialEq for Relation