struct.discriminatedUnion (@defjs/core)

@defjs/core · Function

Signature

function discriminatedUnion<
  const TDiscriminator extends string,
  const TOptions extends readonly [
    ObjectStruct<ObjectShape>,
    ...ObjectStruct<ObjectShape>[],
  ],
>(
  discriminator: TDiscriminator,
  options: TOptions & RequiredDiscriminatorOptions<TDiscriminator, TOptions>,
): DiscriminatedUnionStruct<TOptions>;

const Event = struct.discriminatedUnion("kind", [
  struct.object({ kind: struct.literal("created"), id: struct.number() }),
  struct.object({ kind: struct.literal("deleted"), id: struct.number() }),
]);

Every option must be an object struct whose discriminator field is a required struct.literal(). A missing field, a non-literal field, an optional field, or a duplicate tag value throws TypeError when the struct is created.
The input must be a plain object. The tag value selects the option, and that option parses the whole object.
A missing tag fails with missing_key, and an unknown tag fails with invalid_union. Both report the tag field's path. Other failures come from the selected option.
With struct.parse(..., { aliases: true }) the tag is read from the field's alias.

RequiredDiscriminatorOptions and DiscriminatedUnionStruct are not exported. The type check rejects an option whose tag field is missing or may be undefined.

Parameters

Prop

Type

discriminator TDiscriminator

options TOptions & RequiredDiscriminatorOptions<TDiscriminator, TOptions>