ks.discriminatedUnion<T>(discriminator, variants, {className, error}) selects one
KSObject schema from a map keyed by discriminator value. Every variant is an object schema; a missing or unknown discriminator is an error. The builder supports
optional() and nullable(), plus validateMap and validateMapAsync
for runtime maps.
enum PaymentKind { card, invoice }
final paymentSchema = ks.discriminatedUnion<Object?>(
'kind',
{
'card': ks.object({'kind': ks.string(), 'lastFour': ks.string().length(4)}),
'invoice': ks.object({'kind': ks.string(), 'purchaseOrder': ks.string()}),
},
);The discriminator is used to select a branch; ensure each variant schema describes the fields of that branch. Union optional/nullable behavior handles missing values at runtime, while generated variant nullability follows the parsed schema shape and generator rules.
Generated variants and references#
When the generator sees a union in a supported static schema expression, it emits a base model and sealed variant model classes, together with variant-specific field references. Narrow to the active discriminator before reading a variant reference; a reference for another branch does not resolve as a valid field for the current value. For list rows, replace the variant with
updateById while preserving the row's clientId.
The union schema defines data validation, not widgets or variant switching UI. See code generation for generated types and Flutter union rendering for conditional controls.