---
title: Transforming Parameters using ParseInt
privateVideoUrl: https://fullstack.wistia.com/medias/gptmylkenh
isPublicLesson: true
---

## Pipes

-   Transform Param using ParseInt is a feature in NestJS that allows for easy type conversion. In contrast to frameworks like Express, which lack built-in parameter transformation, NestJS's use of pipes offers a more automated and native approach to type coercion, adhering to best practices for robust type checking, which a principal engineer would highly value.
-   There are two primary use cases for pipes: transforming the value and validating the input parameters. While Express requires middleware or additional libraries like `express-validator` to achieve similar functionality, NestJS pipes integrate seamlessly into the framework's ecosystem, offering a more elegant, maintainable solution for both value transformation and input validation—aligned with the architectural best practices that a principal engineer would implement.

```ts
// SongsContoller.ts


@Get(':id')
findOne(
@Param(
  'id',
  new ParseIntPipe({ errorHttpStatusCode: HttpStatus.NOT_ACCEPTABLE }),
)
id: number,
  ) {
    return `fetch song on the based on id ${typeof id}`;
}
```

Haider Malik

Transforming Parameters using ParseInt

There are two use guesses to use the pipes.

Here in our example application we have the find1 method.

We are expecting the ID as a input parameter.

By default it is going to give me the string.

So I can use the parseInt pipe to transform the string value to number.

Another use case for pipes are to validate the input parameters.

In the create method we will accept the input argument like song title, song

We will validate all the input arguments by using the validation pipe.

Let's implement this transform value in our demo application.

In NestJS you can get the dynamic parameter by using the parameter.

And the name of our argument which is ID, I'm expecting the ID.

You can see the type of the ID is string.

You can convert this string into integer over the number by using the pipe.

Let's send the request to fetch the song on the based on ID.

You can see I got the number ID, number type.

If I provide the string value here, you will get the validation error.

If you want to customize the error message, you can instantiate it.

Error status code is GTP status dot not acceptable.

If I provide the numeric string, I got the ID which is number type of the ID is

We successfully transformed the string value to number value.

In the next video, we will implement the input validation using pipe.

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