[英]What is wrong with Inheritance in Typescript?
Typescript 中的 inheritance 有什么问题?
我创建了这个 class:
export class ExtendedService<T extends ExtendedEntity> {
protected repository: Repository<T>;
constructor(
repository?: Repository<T>
){
this.repository = repository;
}
public async create(data: DeepPartial<T>): Promise<T> {
const entity: T = this.repository.create(data);
return entity.save();
}
}
并在此扩展此 class :
@Injectable()
export class UserService extends ExtendedService<UserEntity> {
constructor(
protected readonly repository: Repository<UserEntity>
){
super();
}
public async register(data: DeepPartial<UserEntity>): Promise<UserEntity> {
const user = new UserEntity();
user.createdAt = new Date();
user.firstName = data.firstName;
user.lastName = data.lastName;
user.email = data.email;
user.role = UserRole.USER;
user.isDeleted = false;
const salt = await genSalt(10);
user.password = await hash(data.password, salt);
return await this.create(user);
}
}
但是在启动这个 function 之后,我的控制台向我抛出了这个:
[Nest] 19980 - 2020-06-29 17:30:56 [ExceptionsHandler] Cannot read property 'create' of undefined +1378ms
TypeError: Cannot read property 'create' of undefined
at Repository.create (C:\Users\Piotruś\Desktop\auth\node_modules\typeorm\repository\Repository.js:49:29)
at UserService.create (C:\Users\Piotruś\Desktop\auth\dist\helpers\service\extended-service.js:27:40)
at UserService.register (C:\Users\Piotruś\Desktop\auth\dist\user\user.service.js:34:27)
at async UserController.register (C:\Users\Piotruś\Desktop\auth\dist\user\user.controller.js:25:9)
at async C:\Users\Piotruś\Desktop\auth\node_modules\@nestjs\core\router\router-execution-context.js:46:28
at async C:\Users\Piotruś\Desktop\auth\node_modules\@nestjs\core\router\router-proxy.js:9:17
所以,问题出在 ts inheritance 中,谁能告诉我我的 inheritance 出了什么问题?
您没有将repository
参数传递给您的基础 class。 在构造函数中调用super()
时,必须提供所有基本 class arguments。
@Injectable()
export class UserService extends ExtendedService<UserEntity> {
constructor(
protected readonly repository: Repository<UserEntity>
){
super(repository);
}
...
}
正如您在此娱乐中看到的那样,将基类存储库参数设为强制性会导致 Typescript 引发编译错误:
预期为 1 arguments,但得到 0。
除非必要,否则我建议您避免将 arguments 设为可选,如果这样做,请采取预防措施以进行必要的 null 检查。
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