Dependency injection basics 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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Aservice

BCatsService

CcatsService

DCats

Attempts:

3 left

💡 Hint

Common Mistakes

Using the class name instead of a variable name.

Using a variable name that does not match the service.

The injected service variable name should start with a lowercase letter and match the service type.

2fill in blank

medium

Complete the code to mark the service as injectable.

NestJS

@[1]()
export class CatsService {}

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AInjectable

BController

CModule

DComponent

Attempts:

3 left

💡 Hint

Common Mistakes

Using @Controller or @Module instead of @Injectable.

Forgetting to add the decorator.

The @Injectable() decorator marks a class as available for dependency injection.

3fill in blank

hard

Fix the error in the provider registration.

NestJS

@Module({
  providers: [[1]],
})
export class CatsModule {}

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ACatsService()

BCatsService

CcatsService

Dnew CatsService()

Attempts:

3 left

💡 Hint

Common Mistakes

Calling the service as a function in providers.

Using an instance instead of the class.

Providers are registered by class reference, not by calling or instantiating them.

4fill in blank

hard

Fill both blanks to inject and use the service in the controller.

NestJS

constructor(private readonly [1]: [2]) {}

getCats() {
  return this.catsService.findAll();
}

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AcatsService

BCatsService

Ccats

DCatService

Attempts:

3 left

💡 Hint

Common Mistakes

Mismatching variable name and type.

Using incorrect service class name.

The constructor parameter name should be catsService and its type CatsService to inject properly.

5fill in blank

hard

Fill all three blanks to create a provider with a custom value and inject it.

NestJS

const customProvider = {
  provide: '[1]',
  useValue: [2],
};

constructor(@Inject('[3]') private readonly config: any) {}

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ACONFIG_OPTIONS

B{ apiKey: '12345' }

DCONFIG

Attempts:

3 left

💡 Hint

Common Mistakes

Mismatching the provide and inject tokens.

Using incorrect object syntax for useValue.

The provider token and the injection token must match exactly. The value is the custom object provided.