Validate request parameters with the class validator

"class-transformer": "^0.5.1",
"class-validator": "^0.14.0"

import { ValidationPipe } from "@nestjs/common";

// ...
app.useGlobalPipes(new ValidationPipe());

---
title: Validate request body with the class-validator
privateVideoUrl: https://fullstack.wistia.com/medias/jheivap4o2
isPublicLesson: true
---

## Validate request parameters with the class validator

-   To validate request parameters, class-validator is often used in NestJS. Installing two required packages initiates this feature, making validation an integral part of the request-handling process, unlike in Express where validation logic might be manually coded or pulled in via additional middleware.
-   Utilizing class-validator in NestJS allows for declarative validation rules in DTO (Data Transfer Object) classes using various decorators such as `@IsString()` or `@IsNotEmpty()`. This approach promotes reusability and maintainability of validation logic, aligning with best practices for scalable application architecture, whereas in Express, separate validation libraries like `validator` or `express-validator` are often needed.

```json
"class-transformer": "^0.5.1",
"class-validator": "^0.14.0"
```

### Global Scope pipes

-   The next action involves binding the `ValidationPipe` from the `@nestjs/common` package. This feature provides an advantage over frameworks like Express, where validation often necessitates additional libraries or custom middleware. In NestJS, pipes offer multiple scopes for validation: parameter-scoped, method-scoped, controller-scoped, or global-scoped, lending greater flexibility and modularity to the application.
-   Opting for a global scope requires registration in the `main.ts` file. This is a best practice for ensuring application-wide consistency in validation, as it minimizes the chances of missing validation logic in any part of the application. Unlike Express, which would require a global middleware function for similar functionality, NestJS makes it straightforward to set global validation rules.

Haider Malik

Validate request body with the class-validator

In this video, I'm gonna teach you how to validate the request body.

When you send request to the local host fallen 3000 3000/song, we are trying to

But let's say if I miss the title field, it is going to give me the validation

The title should not be empty and title must be string.

Now you can see title should not be empty and artist should not be empty.

So I would like to add this validation to our create new song AP endpoint.

When you go to the Spotify, if I click on any song, this is the title of the

this is the published date or the least date and this is the duration.

So we're gonna pick title, duration and the date of the song.

Let's install the class validator package and we also need class transformer.

You can see both packages have installed.

You can use validation pipe for specific controller method.

You can use it here or you can use it here.

It's your choice but I'm gonna create a global.

I'm gonna register it as a global so I can use in any controller.

There is a method which is use global pipes.

Nest yes already created the validation pipe.

I have imported the validation pipe from Nest yes common package.

And now if you don't have DTO which is data transfer object, you have to

Now we need to add decorator based validations.

Let's create a new class and I'm gonna name it to create song DTO.

I'm gonna make it read only and we have the second property which is artist

Then we have another property which is released it.

Or you can specify the type which is string and the type of artist it's an

This is another property which is duration.

We need to store the duration in the time format.

Now I'm gonna use the decorator from class validator the type of title should

and it's a required property so you can say it's not an empty.

We can follow the same stuff for artist not empty.

Let's add decoration decorator for release date type should be string and class

Now we have if you want to store the time or add evaluation for the time there

which is military time and it's also required property so I'm gonna add is not

So is it string if you want to apply that you have to add to date in this

Now we're gonna apply we have already registered validation pipe here and we

transfer object which is create song video.

Now I would like to apply this create song dto in the create endpoint.

You can register it or you can apply it by using the body parameter.

Please apply it on the request body and I can say create song.

Create song dto the type is create song dto and this time I'm gonna push create

Let's try to test it out and we need to run the application.

So we have to send the request or add the JSON body in the response.

Let me open the restaurant dot HTTP file and we need to add the JSON body.

You can see title should not be empty title must be string artist should not be

So validations have applied successfully.

I can say last thing level the title and we need the artist.

If you will add date in different format.

You can see that should be valid ISO 860 date string format.

Devolution must be valid representation of military time which is ours and

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