Entity definition in NestJS - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a basic entity class with a decorator.

NestJS

import { [1] } from 'typeorm';

@Entity()
export class User {
  @PrimaryGeneratedColumn()
  id: number;

  @Column()
  name: string;
}

Drag options to blanks, or click blank then click option'

AController

BEntity

CModule

DInjectable

Attempts:

3 left

💡 Hint

Common Mistakes

Using @Controller or @Module instead of @Entity

Forgetting to import the decorator from 'typeorm'

The @Entity() decorator marks the class as a database entity in TypeORM, which NestJS uses for database models.

2fill in blank

medium

Complete the code to define a primary key column in the entity.

NestJS

import { Entity, [1], Column } from 'typeorm';

@Entity()
export class Product {
  @[1]()
  id: number;

  @Column()
  title: string;
}

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APrimaryGeneratedColumn

BPrimaryColumn

CGenerated

DCreateDateColumn

Attempts:

3 left

💡 Hint

Common Mistakes

Using @PrimaryColumn without generation

Confusing with @CreateDateColumn which is for timestamps

@PrimaryGeneratedColumn() creates a primary key column with auto-generated values, commonly used for IDs.

3fill in blank

hard

Fix the error in the entity property decorator to correctly define a string column.

NestJS

import { Entity, PrimaryGeneratedColumn, Column } from 'typeorm';

@Entity()
export class Category {
  @PrimaryGeneratedColumn()
  id: number;

  @Column({ type: '[1]' })
  name: string;
}

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Avarchar

Binteger

Cboolean

Ddate

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'integer' or 'boolean' for string fields

Leaving type undefined causing default assumptions

The varchar type is used for string columns in SQL databases, which matches the string type in TypeScript.

4fill in blank

hard

Fill both blanks to define a nullable column with a default value.

NestJS

import { Entity, PrimaryGeneratedColumn, Column } from 'typeorm';

@Entity()
export class Post {
  @PrimaryGeneratedColumn()
  id: number;

  @Column({ [1]: true, [2]: 'draft' })
  status: string;
}

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Anullable

Bdefault

Cunique

Dlength

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'unique' or 'length' instead of 'nullable' or 'default'

Forgetting to set nullable true for optional fields

nullable: true allows the column to have null values. default: 'draft' sets the default value when none is provided.

5fill in blank

hard

Fill all three blanks to define a one-to-many relationship between entities.

NestJS

import { Entity, PrimaryGeneratedColumn, Column, [1], [2], [3] } from 'typeorm';

@Entity()
export class Author {
  @PrimaryGeneratedColumn()
  id: number;

  @Column()
  name: string;

  @[1](() => Post, post => post.author)
  posts: Post[];
}

@Entity()
export class Post {
  @PrimaryGeneratedColumn()
  id: number;

  @Column()
  title: string;

  @[2](() => Author, author => author.posts)
  @[3]()
  author: Author;
}

Drag options to blanks, or click blank then click option'

AOneToMany

BManyToOne

CJoinColumn

DManyToMany

Attempts:

3 left

💡 Hint

Common Mistakes

Using ManyToMany instead of OneToMany/ManyToOne

Forgetting to import JoinColumn or use it on the owning side

OneToMany and ManyToOne decorators define the two sides of a one-to-many relationship. JoinColumn is used on the many-to-one side to specify the owning side of the relation.