AdditionalProperties

@tsed/schema

Usage

import { AdditionalProperties } from "@tsed/schema";

See /packages/specs/schema/src/decorators/common/additionalProperties.ts.

Overview

function AdditionalProperties(schema: boolean | AnyJsonSchema): (...args: any[]) => any;

• schema (boolean | AnyJsonSchema): - Boolean to allow/disallow additional properties, or a schema they must match

Description

Controls whether additional properties beyond those defined in the schema are allowed.

By default, JSON Schema validation may allow properties not explicitly defined in the schema. This decorator lets you control that behavior either by disabling additional properties entirely or by specifying a schema that additional properties must conform to.

Usage with boolean

// Disallow any additional properties
@AdditionalProperties(false)
class StrictModel {
  @Property()
  name: string;
  // Any other properties will cause validation errors
}

// Explicitly allow additional properties (default behavior)
@AdditionalProperties(true)
class FlexibleModel {
  @Property()
  name: string;
  // Additional properties are allowed
}

Usage with schema

// Additional properties must be strings
@AdditionalProperties({ type: "string" })
class DynamicModel {
  @Property()
  id: number;
  // Other properties must be strings
}

// Additional properties must match a complex schema
@AdditionalProperties({
  type: "object",
  properties: {
    value: { type: "string" }
  }
})
class MetadataModel {
  @Property()
  name: string;
  // Additional properties must be objects with a 'value' string property
}

Common Use Cases

• Strict APIs: Use @AdditionalProperties(false) to ensure clients only send expected fields
• Dynamic Data: Use with a schema to validate dynamic property values
• Migration: Allow additional properties during API versioning transitions