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Question

我在 nodejs 和 typescript 中有一个项目。 我正在使用 mongoose 连接到 mongoDb 数据库。 我的代码看起来像这样

import { Schema, Document, Model } from 'mongoose';
import * as mongoose from 'mongoose';

export interface IProblem extends Document {
  problem: string;
  solution: string;
}

const ProblemSchema = new Schema({
  problem: { type: String, required: true },
  solution: { type: String, required: true },
});

export async function findOneByProblem(
  this: IProblemModel,
  { problem, solution }: { problem: string; solution: string }
): Promise<IProblem> {
  const record = await this.findOne({ problem, solution });
  return record;
}

export default mongoose.model('Problem', ProblemSchema);

ProblemSchema.statics.findOneByProblem = findOneByProblem;

export interface IProblemModel extends Model<IProblem> {
  findOneByProblem: (
    this: IProblemModel,
    { problem, solution }: { problem: string; solution: string }
  ) => Promise<IProblem>;
}

然而，在这些行

const record = await this.findOne({ problem, solution });
return record;

我收到一个编译器错误说这个

TS2322: Type 'IProblem | null' is not assignable to type 'IProblem'.   Type 'null' is not assignable to type 'IProblem'.

我错过了什么吗？

Answer 1

您的findOneByProblem类型是错误的 – 毕竟，您可能没有找到IProblem实例，结果为空。

正确的类型是

Promise<IProblem | null>

– 或者你可以在内部if(problem === null) throw new Error("No Problem found"); 如果您不想更改类型，则可以在函数中使用或类似。