Class-validator - validate array of objects - arrays

Question

I am using class-validator package with NestJS and I am looking to validate an array of objects that need to have exactly 2 objects with the same layout:
So far I have:
import { IsString, IsNumber } from 'class-validator';
export class AuthParam {
#IsNumber()
id: number;
#IsString()
type: string;
#IsString()
value: string;
}
and
import { IsArray, ValidateNested } from 'class-validator';
import { AuthParam } from './authParam.model';
export class SignIn {
#IsArray()
#ValidateNested({ each: true })
authParameters: AuthParam[];
}
per #kamilg response (I am able to enforce exacly 2 elements):
import { IsArray, ValidateNested, ArrayMinSize, ArrayMaxSize } from 'class-validator';
import { AuthParam } from './authParam.model';
export class SignInModel {
#IsArray()
#ValidateNested({ each: true })
#ArrayMinSize(2)
#ArrayMaxSize(2)
authParameters: AuthParam[];
}
I still can pass an empty array or an array with some other objects not related to AuthParam.
How I should modify it get validation?
Also how I can enforce mandatory 2 elements in the array? MinLength(2) seems to be regarding string... (resolved)

Answer 1

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.

Answer 2

I Know I Am Late But Facing Some Issue With Type, Then Try Another Way To Implement This:
export class AuthParam {
#IsNumber()
id: number;
#IsString()
type: string;
#IsString()
value: string;
}
Validation function
#ValidatorConstraint()
export class IsAuthArray implements ValidatorConstraintInterface {
public async validate(authData: AuthParam[], args: ValidationArguments) {
return Array.isArray(authData) && authData.reduce((a, b) => a && (typeof b.id === "number") && typeof b.type === "string" && typeof b.field === "string", true);
}
}
export class SignInModel {
#IsNotEmpty()
#IsArray()
#ArrayMinSize(2)
#ArrayMaxSize(2)
#Validate(IsAuthArray, {
message: "Enter valid value .",
})
authParameters: AuthParam[];
}
Maybe It Will Help Someone 😃

Answer 3

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.

Answer 4

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)