Struct TriggerPredicate 

pub struct TriggerPredicate {
    pub field: String,
    pub eq: Option<Value>,
    pub changed_to: Option<Value>,
}

A single declarative field/transition predicate on an after:mutation trigger (#597).

The when condition that decides whether a function fires, evaluated by the dispatcher against the built payload before any runtime spins.

Deliberately small: a field plus exactly one operator — eq (state) or changed_to (transition). Anything richer stays guest code; this is a dispatch filter, not a rules engine. A list of predicates is a conjunction (all must hold); an empty list always fires (back-compat).

{ "field": "status", "changed_to": "approved" }  // UPDATE-only transition test
{ "field": "kind",   "eq": "standard" }           // state test (INSERT + UPDATE)

Fields

field: String

The field (a JSON key in the row image) to test.

eq: Option<Value>

State test: the field currently equals this value. Evaluated on the after-image (INSERT/UPDATE) or, for a DELETE, the pre-image. An absent field never equals a value (missing ⇒ false).

changed_to: Option<Value>

Transition test (UPDATE-only): the field changed to this value — old.field != v && new.field == v. A DELETE (no after-image) never matches; changed_to on a non-update trigger is a load error.

Implementations

impl TriggerPredicate

pub fn matches(&self, old: Option<&Value>, new: Option<&Value>) -> bool

Evaluate this predicate against a row’s old/new images.

• eq: the current image (new, or old on a DELETE) has field == v. Missing field ⇒ false.
• changed_to: old.field != v && new.field == v.

A predicate with neither operator set (rejected at load) never matches.

pub fn validate(&self, operation: Option<&str>) -> Result<(), String>

Validate the predicate at load time against the trigger’s operation (insert/update/delete, or None for all).

Errors

• Neither eq nor changed_to set, or both set (exactly one operator).
• changed_to on a non-update trigger (a transition needs a before + after).

Trait Implementations

impl Clone for TriggerPredicate

fn clone(&self) -> Self

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for TriggerPredicate

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

Formats the value using the given formatter.

impl<'de> Deserialize<'de> for TriggerPredicate

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

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl Eq for TriggerPredicate

impl PartialEq for TriggerPredicate

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

Equality operator ==.

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

Inequality operator !=.

impl Serialize for TriggerPredicate

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 TriggerPredicate