所以我的问题是，如何检查运行this.userService.findOne(createUserDto.username);时是否没有结果？

控制器：

import { Get, Controller, Body, Post, Param } from "@nestjs/common";
import { RegisterService } from "./register.service";
import * as bcrypt from "bcrypt";
import { CreateUserDto } from "./create-user.dto";

@Controller("register")
export class RegisterController {
  constructor(private userService: RegisterService) {}

  @Post()
  create(@Body() createUserDto: CreateUserDto) {
    let chkUname: any = this.userService.findOne(createUserDto.username);

    let response = {
      usernError: "",
      regOk: true,
    };

    if (!chkUname) {
      // this.userService.createUser(createUserDto);
      return chkUname;
    } else {
      // response.usernError = "Sorry, this username is used!";
      // response.regOk = false;
      return true;
    }
  }
  // create(@Param("uname") uname: any) {
  //   return this.userService.findOne(uname);
  // }
}

服务：

import { Injectable, NotFoundException } from "@nestjs/common";
import { InjectModel } from "@nestjs/mongoose";
import { Model } from "mongoose";
import { CreateUserDto } from "./create-user.dto";
import { Users, UsersDocument } from "./schema/user.schema";

@Injectable()
export class RegisterService {
  constructor(
    @InjectModel(Users.name) private readonly usersModel: Model<UsersDocument>
  ) {}

  async createUser(createUserDto: CreateUserDto): Promise<UsersDocument> {
    const user = new this.usersModel(createUserDto);
    return user.save();
  }

  async findOne(uname: string) {
    return this.usersModel.find({uname}).exec();
  }
}

它总是返回true/false，这取决于我编写的代码。