how to write dto and schema for array in nest js?

Question

{
    "studentRollNo": 1,
    "firstName": "name",
    "class": "second standard",
    "subjects": [
        {
            "sNo": "1.1",
            "name": "social",
            "marks": "89",
            "questionsAttempted": "100%"
        },
        {
            "sNo": "1.2",
            "name": "mathematics",
            "marks": "69",
            "questionsAttempted": "100%"
        }
    ]
}

Answer 1

Here is an example scheme using mongoose class-transformer and swagger

@Schema({ timestamps: true })
export class Example {
  @ApiHideProperty()
  @Prop({ type: SchemaTypes.ObjectId, default: Types.ObjectId })
  @Exclude()
  _id: Types.ObjectId;

  @ApiHideProperty()
  @Exclude()
  __v: number;

  @Prop({ type: Number, required: true })
  studentRollNo: number;

  @Prop({ type: String, required: true })
  firstName: string;

  @Prop({ type: String, required: true })
  class: string;

  @Prop(
    raw([
      {
        sNo: { type: Number, required: true },
        name: { type: String, required: true },
        marks: { type: String, required: true },
        questionsAttempted: { type: String, required: true },
      },
    ]),
  )
  subjects: {
    sNo: number;
    name: string;
    marks: string;
    questionsAttempted: string;
  }[];

  @ApiProperty()
  @Expose()
  get id(): string {
    return String(this._id);
  }
}

export const ExampleSchema = SchemaFactory.createForClass(Example);

and DTO

export class SubjectDto {
  sNo: number;

  name: string;

  marks: string;

  questionsAttempted: string;
}

export class ExampleDto {
  studentRollNo: number;

  firstName: string;

  class: string;

  subjects: SubjectDto[];
}

You can also add validation to these dtos using class-validator For validation "subject", use the validation you need in SubjectDto and add @ValidationNested({each: true}) to subjest field in ExampleDto

Please mark this answer as correct if it helped you