TypeORM find返回类型与定义的Student实体类型不匹配问题求助

问题代码 #

import { Student } from "core"
import { Repository } from "./Repository"
import { Database } from "../../db"
export class UserRepository<Student> extends Repository<Student> {
    private _repository = Database.AppDataSource.getRepository(Student);
    public override async GetById (id: number): Promise<Student | null> {
        return await this._repository.findOneBy({ id: id });
    }
    public override async ListAll (): Promise<Student[]> {
        return await this._repository.find();
    }
}

说明：Student 类型定义在 core 模块中

构建错误信息 #

Data/Repositories/StudentRepository.ts:7:9 - error TS2322: Type 'import("/usr/src/Node.JSRestAPI/src/core/build/index").Student | null' is not assignable to type 'Student | null'.
  Type 'import("/usr/src/Node.JSRestAPI/src/core/build/index").Student' is not assignable to type 'Student'.
    'Student' could be instantiated with an arbitrary type which could be unrelated to 'import("/usr/src/Node.JSRestAPI/src/core/build/index").Student'.

7         return await this._repository.findOneBy({ id: id });
          ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Data/Repositories/StudentRepository.ts:10:9 - error TS2322: Type 'import("/usr/src/Node.JSRestAPI/src/core/build/index").Student[]' is not assignable to type 'Student[]'.
  Type 'import("/usr/src/Node.JSRestAPI/src/core/build/index").Student' is not assignable to type 'Student'.
    'Student' could be instantiated with an arbitrary type which could be unrelated to 'import("/usr/src/Node.JSRestAPI/src/core/build/index").Student'.

10         return await this._repository.find();
           ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

错误原因 #

你在定义 UserRepository 时，把 Student 声明成了泛型参数，这会覆盖从 core 模块导入的 Student 类型。此时类中的 Student 不再是你导入的具体类型，而是一个可被任意类型替换的泛型占位符，导致 TypeScript 无法识别它与数据库返回的 Student 类型一致，从而抛出类型不匹配错误。

解决方案 #

移除类定义中的泛型参数 <Student>，直接使用从 core 模块导入的 Student 类型：

import { Student } from "core"
import { Repository } from "./Repository"
import { Database } from "../../db"
// 移除泛型参数 <Student>，直接为基类 Repository 指定具体类型 Student
export class UserRepository extends Repository<Student> {
    private _repository = Database.AppDataSource.getRepository(Student);
    public override async GetById (id: number): Promise<Student | null> {
        return await this._repository.findOneBy({ id: id });
    }
    public override async ListAll (): Promise<Student[]> {
        return await this._repository.find();
    }
}

如果 Repository 基类本身是泛型类，只需在继承时传入导入的 Student 类型即可，无需将 Student 重新声明为当前类的泛型参数。

内容的提问来源于stack exchange，提问作者khteh