additionalProperties property

Rules for additional properties that don't match the properties or patternProperties schemas.

Can be either a bool or a Schema, if it is a Schema then additional properties should match that Schema.

For example, to define a schema where any property not explicitly defined in properties should have an integer value:

final schema = ObjectSchema(
  properties: {'name': Schema.string()},
  additionalProperties: Schema.int(),
);

In this schema, an object like {'name': 'John', 'age': 30} would be valid, but {'name': 'John', 'age': 'thirty'} would be invalid because age is not a defined property and its value is not an integer as required by additionalProperties.