How to transform input data with NestJS and TypeORM

Question

I want to create functionality where I can transform incoming data before it hits the database. Let's say that we want to make sure that when a new user is created, the firstName and lastName attribute values are always starting with a capital letter. Or another great example is to prevent login issues and store email addresses always in lowercase letters.

I've taken a look at the pipe documentation of NestJS but it's too generic. I want to be able to specify which fields need transformation and I don't want to create a pipe for each attribute or endpoint that needs transformation.

I've also tried the @Transform decorator form the 'class-transformer' package but this doesn't seem to work.

export class UserRoleCreateDto {
  @IsDefined()
  @IsString()
  @IsNotEmpty()
  @Transform((name) => name.toUpperCase())
  readonly name;
}

The expected result should be the name in uppercase letters but it's not.

Anyone any ideas or examples on how to implement proper input transformation for NestJS / TypeORM before it hits the database?

Thanks for your time!

Answer 1

You can also use TypeORM's entity listeners.

@BeforeInsert

You can define a method with any name in entity and mark it with @BeforeInsert and TypeORM will call it before the entity is inserted using repository/manager save.

@Entity()
export class User {
    
    @BeforeInsert()
    nameToUpperCase() {
        this.email = this.email.toLowerCase()
        this.name = this.name.toUpperCase();
    }
}

Source here