Resolvers in NestJS - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a basic GraphQL resolver method.

NestJS

import { Resolver, Query } from '@nestjs/graphql';

@Resolver()
export class SampleResolver {
  @Query(() => String)
  hello() {
    return [1];
  }
}

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

Aconsole.log('Hello World!')

BHello World!

C'Hello World!'

Dreturn 'Hello World!'

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting quotes around the string

Using console.log instead of return

Returning a non-string value

The resolver method should return a string value. The correct syntax is to return a string literal like 'Hello World!'.

2fill in blank

medium

Complete the code to inject a service into the resolver constructor.

NestJS

import { Resolver } from '@nestjs/graphql';
import { SampleService } from './sample.service';

@Resolver()
export class SampleResolver {
  constructor(private readonly [1]: SampleService) {}
}

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

Asample_service

Bservice

CSampleService

DsampleService

Attempts:

3 left

💡 Hint

Common Mistakes

Using the class name with uppercase first letter as variable

Using underscores in variable names

Using generic names like 'service'

The injected service should be named in camelCase, typically matching the service class name but starting with a lowercase letter.

3fill in blank

hard

Fix the error in the resolver method decorator to correctly define a mutation.

NestJS

import { Resolver, [1] } from '@nestjs/graphql';

@Resolver()
export class SampleResolver {
  @[1](() => Boolean)
  async updateData() {
    return true;
  }
}

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

AMutation

BSubscription

CQuery

DResolveField

Attempts:

3 left

💡 Hint

Common Mistakes

Using @Query instead of @Mutation

Using @Subscription for mutations

Forgetting to import the decorator

To define a mutation in a GraphQL resolver, use the @Mutation decorator imported from '@nestjs/graphql'.

4fill in blank

hard

Fill both blanks to define a resolver method that accepts an argument.

NestJS

import { Resolver, Query, Args } from '@nestjs/graphql';

@Resolver()
export class SampleResolver {
  @Query(() => String)
  greet(@[1]('name') [2]: string) {
    return `Hello, ${name}!`;
  }
}

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AArgs

Bname

CArg

Dusername

Attempts:

3 left

💡 Hint

Common Mistakes

Using @Arg instead of @Args

Mismatching argument and parameter names

Forgetting the decorator

The @Args decorator is used to get arguments from the query, and the parameter name should match the argument name.

5fill in blank

hard

Fill all three blanks to create a resolver method that returns a list of items filtered by a minimum value argument.

NestJS

import { Resolver, Query, Args } from '@nestjs/graphql';

@Resolver()
export class SampleResolver {
  @Query(() => [Number])
  getNumbers(@[1]('min') [2]: number) {
    const numbers = [1, 5, 10, 20];
    return numbers.filter(n => n [3] min);
  }
}

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

AArgs

Bmin

C>=

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' instead of '>=' in filter

Mismatching argument and parameter names

Forgetting the @Args decorator

Use @Args to get the 'min' argument, name the parameter 'min', and filter numbers greater than or equal to min.