CODEWITHSUNDEEP
nestjsclass-validatorclass-transformer
barley
barley

Reputation: 196

Get a value before implicit transformation is performed in class-transformer

I am trying to convert a GET parameter to a boolean value. I am using NestJS with class-validator and class-transformer. I have set enableImplicitConversion to true in the validator pipe options.

class ExampleDto {
  @Transform(value => value === 'true')
  prop1: boolean;
}

Now the issue is, the GET parameter's value is always string, so the implicit transformation will always convert it to true. I can prevent it by running a custom logic, but the implicit transformation is being performed before i can run any custom logic (i.e. the @Transform decorator).

Is there any way to get the value before it has been transformed?

or, Is there any other way I can achieve what I am trying to achieve? (eg. disable implicit conversion for a property, etc)

Upvotes: 2

Views: 2497

Answers (3)

Abdulghani Albaik
Abdulghani Albaik

Reputation: 35

As @barley said the "obj" parameter it solves your problem.

So the "Transform" decorator will be like this:

class ExampleDto {
  @Transform(({ obj }) => JSON.parse(obj.prop1))
  prop1: boolean;
}

Upvotes: 0

iambinodstha
iambinodstha

Reputation: 1007

you need to implicitly check whether the Boolean string is true or false. if that doesn't match the condition return the original string value.

class ExampleDto {
  @IsBoolean()
  @Transform(({ value} ) => value === 'true' ? true : value === 'false' ? false : value)
  prop1: boolean;
}

Upvotes: 0

barley
barley

Reputation: 196

I figured it out.

The function we pass to @Transform decorator takes 3 parameters. One of them is the original object (without transformation).

Upvotes: 2

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