Why can't I change the entity's constructor in typeorm-CodePudding

I'm fairly new to Typeorm and typescript. I've been using it like so for now :

export class Actor extends BaseEntity {

  @Column()
  name: string

  @Column()
  age: number

}

let actor = new Actor()
Object.assign(actor, { name: "John Doe", age: 50 })
await actor.save()

let actors = Actor.find()

It work great for now. I use Object.assign because if I receive it as input from the user with 30 fields, it's much more convenient than if I had to do it manually. However, I was hoping to be able to simplify it further by including it in the constructor so I don't have to do it everytime :

export class Actor extends BaseEntity {

  constructor(obj){
    super()
    Object.assign(this, obj)
  }

  @Column()
  name: string

  @Column()
  age: number

}

let actor = new Actor({ name: "John Doe", age: 50 })
await actor.save()

let actors = Actor.find()

I would have expected it to work without issues but I get a very weird one that I can't seem to understand on the let actors = Actor.find() line :

The 'this' context of type 'typeof Actor' is not assignable to method's 'this' of 
type '(new () => Actor) & typeof BaseEntity'.
  Type 'typeof Actor' is not assignable to type 'new () => Actor'.
    Types of construct signatures are incompatible.
      Type 'new (obj: any) => Actor' is not assignable to type 'new () => Actor'.ts

I'm assuming it's due to the amount of arguments changing in the constructor but it's not like an interface can indicates what the constructor should look like so I'm a bit lost as why this happens and what do I misunderstand there

CodePudding user response：

You're getting an error because your Actor entity now expects one argument, but TypeORM won't pass any arguments to it (which is unsound, imagine expecting a cake and then not getting a cake; how sad). You can probably get around this by making the parameter optional (defaulting to {}):

export class Actor extends BaseEntity {

  constructor(obj = {}) {
    super()
    Object.assign(this, obj)
  }

  @Column()
  name: string

  @Column()
  age: number

}

but in any case you really shouldn't be changing the entity class. Maybe you could play around with the idea of a builder instead?

new ActorBuilder().setName(...).setAge(...).build() // returns Actor

or a helper function:

createActor({ ... }) // returns Actor

It's probably best not to modify the entity class. You don't really know what TypeORM is doing under the hood (unless you are a contributor, of course :D) so I would keep the entity class as-is.