CODEWITHSUNDEEP
nestjstypeorm
Ashish Choubey
Ashish Choubey

Reputation: 457

Common columns for all entity in nestjs

let say there are different entity User, Role, Task

All these entities have createdBy, updatedBy, createdOn, updatedOn in common.

I want to know how can I create a base entity such that all entity extends base class in nest js using Typeform.

Upvotes: 4

Views: 6500

Answers (1)

Naor Levi
Naor Levi

Reputation: 1813

This is the place where should you use inheritance.
Basically, the idea is to have a base class/entity that gathers common logic or structure where many other classes/entities share that common logic.

For example: Cat, Dog, Elephant are all having similar characterizations, so we might want to gather all these similar characterizations at a single place in order to avoid duplication of logic and code.

So let's see the simplest example only for basic understanding.

export class Animal {
    protected numberOfLegs: number;
    protected sound(): void;
}

export class Dog extends Animal {
    constructor() {
       super();
       this.numberOfLegs = 4;
    }

    sound(): void {
        console.log('BARK');
    }
}

For your needs:

Export a base entity.

import { Entity, Column } from 'typeorm';

export class BaseEntity {
    @Column()
    createdBy: string;

    @Column()
    updatedBy: string;

    @Column()
    createdOn: Date;

    @Column()
    updatedOn: Date;
}

And then inherit it from derived entities.

import { Entity, Column } from 'typeorm';
import {BaseEntity} from './base-entity';

export class DerivedEntity extends BaseEntity {
    @Column()
    id: string;

    ...
}

Please read about inheritance which is a basic and very important principle in programming and OOP.

Upvotes: 4

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