Constructor injection in NestJS - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to inject the service into the constructor.

NestJS

constructor(private readonly [1]: CatsService) {}

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AcatsService

BCatsService

Cservice

DCats

Attempts:

3 left

💡 Hint

Common Mistakes

Using the class name with uppercase as the property name

Forgetting to mark the property as private readonly

The injected service should be a private readonly property with a camelCase name, usually the service name starting with a lowercase letter.

2fill in blank

medium

Complete the code to declare the service type in the constructor.

NestJS

constructor(private readonly catsService: [1]) {}

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AcatsService

BCats

CService

DCatsService

Attempts:

3 left

💡 Hint

Common Mistakes

Using the instance name instead of the class name as type

Using a generic name like 'Service' instead of the specific service class

The type of the injected service should be the service class name, which is CatsService.

3fill in blank

hard

Fix the error in the constructor injection syntax.

NestJS

constructor([1] catsService: CatsService) {}

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Areadonly

Bprivate readonly

Cpublic

Dprotected

Attempts:

3 left

💡 Hint

Common Mistakes

Omitting access modifiers

Using only 'public' or only 'readonly' without 'private'

To properly inject a service in NestJS, the constructor parameter must be marked private readonly to create and assign the property automatically.

4fill in blank

hard

Fill both blanks to complete the service injection and usage.

NestJS

export class CatsController {
  constructor([1] catsService: CatsService) {}

  findAll() {
    return this.catsService.[2]();
  }
}

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Aprivate readonly

BgetCats

CfetchCats

Dpublic

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'public' instead of 'private readonly' in constructor

Calling a non-existent method like 'fetchCats' if the service method is 'getCats'

The constructor parameter must be private readonly to inject the service. The method called on the service is assumed to be getCats() to fetch all cats.

5fill in blank

hard

Fill all three blanks to define and inject a service, then use it in a method.

NestJS

import { Injectable } from '@nestjs/common';

@Injectable()
export class DogsService {
  getDogs() {
    return ['Bulldog', 'Beagle'];
  }
}

export class DogsController {
  constructor([1] dogsService: [2]) {}

  listDogs() {
    return this.dogsService.[3]();
  }
}

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Aprivate readonly

BDogsService

CgetDogs

Dpublic

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'public' instead of 'private readonly' for injection

Wrong service type or method name

The service is injected with private readonly and typed as DogsService. The method called to get dogs is getDogs().