Class-validator - validate array of objects

Add @Type(() => AuthParam) to your array and it should be working. Type decorator is required for nested objects(arrays). Your code becomes

import { IsArray, ValidateNested, ArrayMinSize, ArrayMaxSize } from 'class-validator';import { AuthParam } from './authParam.model';import { Type } from 'class-transformer';export class SignInModel {  @IsArray()  @ValidateNested({ each: true })  @ArrayMinSize(2)  @ArrayMaxSize(2)  @Type(() => AuthParam)  authParameters: AuthParam[];}

Be careful if you are using any exception filter to modify the error reponse. Make sure you understand the structure of the class-validator errors.

You can use the following:

validator.arrayNotEmpty(array); // Checks if given array is not empty.

validator.arrayMinSize(array, min); // Checks if array's length is at least `min` number.

(https://github.com/typestack/class-validator#manual-validation)

You may want to consider writing custom validator which would better reflect the business requirement you have.

const param1: AuthParam = Object.assign(new AuthParam(), {  id: 1,  type: 'grant',  value: 'password'})const param2: AuthParam = Object.assign(new AuthParam(), {  id: 1,  type: 4,  value: 'password'})const signInTest = new SignInModel()signInTest.authParameters = [param1, param2]validate(signInTest).then(e => {  console.log(e[0].children[0].children[0])})

This works correctly, this is:

ValidationError {  target: AuthParam { id: 1, type: 4, value: 'password' },  value: 4,  property: 'type',  children: [],  constraints: { isString: 'type must be a string' } }

so I may only assume that object which is being validated, is not an instance of AuthParam

const param2: AuthParam = {  id: 1,  type: 4,  value: 'password'} as any

as expected, there aren't any decorators on this object (which may be true for Nest.js controllers and nested objects from body/req) - so validation is ignored.

Please check this (tl;dr - @Type decorator form class-transformer)