如何在NestJS中为数组结构编写DTO与Schema？

我们先处理嵌套的subjects数组结构，不管是DTO还是数据库Schema，都需要先定义子结构，再在父结构中引用。

一、编写DTO（数据传输对象） #

DTO用于验证和转换请求/响应数据，需依赖class-validator和class-transformer包（未安装则执行：npm install class-validator class-transformer）

1. 定义Subject子DTO #

先编写数组内子对象的DTO：

// src/students/dto/subject.dto.ts
import { IsString } from 'class-validator';

export class SubjectDTO {
  @IsString()
  sNo: string;

  @IsString()
  name: string;

  @IsString()
  marks: string;

  @IsString()
  questionsAttempted: string;
}

2. 定义Student父DTO #

在父级DTO中引用SubjectDTO，实现数组结构的验证：

// src/students/dto/student.dto.ts
import { IsNumber, IsString, ValidateNested, ArrayMinSize } from 'class-validator';
import { Type } from 'class-transformer';
import { SubjectDTO } from './subject.dto';

export class StudentDTO {
  @IsNumber()
  studentRollNo: number;

  @IsString()
  firstName: string;

  @IsString()
  class: string;

  @ValidateNested({ each: true }) // 验证数组中的每一个嵌套对象
  @ArrayMinSize(1) // 确保科目数组至少有一个元素
  @Type(() => SubjectDTO) // 指定嵌套对象的类型
  subjects: SubjectDTO[];
}

二、编写Mongoose Schema（用于MongoDB） #

如果使用Mongoose操作MongoDB，需定义对应的Schema，依赖@nestjs/mongoose和mongoose包（未安装则执行：npm install @nestjs/mongoose mongoose）

1. 定义Subject子Schema #

先编写子文档的Schema：

// src/students/schemas/subject.schema.ts
import { Prop, Schema, SchemaFactory } from '@nestjs/mongoose';
import { Document } from 'mongoose';

export type SubjectDocument = Subject & Document;

@Schema()
export class Subject {
  @Prop({ required: true })
  sNo: string;

  @Prop({ required: true })
  name: string;

  @Prop({ required: true })
  marks: string;

  @Prop({ required: true })
  questionsAttempted: string;
}

export const SubjectSchema = SchemaFactory.createForClass(Subject);

2. 定义Student父Schema #

在父级Schema中引用Subject Schema，声明数组类型的字段：

// src/students/schemas/student.schema.ts
import { Prop, Schema, SchemaFactory } from '@nestjs/mongoose';
import { Document } from 'mongoose';
import { Subject, SubjectSchema } from './subject.schema';

export type StudentDocument = Student & Document;

@Schema()
export class Student {
  @Prop({ required: true, unique: true })
  studentRollNo: number;

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

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

  @Prop({ type: [SubjectSchema], required: true }) // 指定为子文档数组
  subjects: Subject[];
}

export const StudentSchema = SchemaFactory.createForClass(Student);

内容的提问来源于stack exchange，提问作者Bhavani Dumpala