NestJS ina uungaji mkono wa daraja la kwanza wa GraphQL kupitia @nestjs/graphql (uliojengwa juu ya Apollo Server). Inatoa mtindo wa code-first (fafanua schema yako kwa TypeScript classes na decorators, schema inazalishwa kiotomatiki) — njia ya kawaida ya NestJS — inayolingana na muundo wa decorator/DI wa framework.
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{}
@ObjectType() // a GraphQL type
export class User {
@Field(() => ID) id: string;
@Field() name: string;
@Field() email: string;
@Field(() => [Post]) posts: Post[]; // related type
}
Katika code-first, classes zenye decorators (@ObjectType, @Field) zinafafanua schema — TypeScript types zinazalisha GraphQL schema kiotomatiki, zikiziweka katika usawazishaji.
@Resolver(() => User)
export class UsersResolver {
constructor(private usersService: UsersService) {} // DI works as usual
@Query(() => [User]) // a query: returns a list of users
users() {
return this.usersService.findAll();
}
@Query(() => User)
user(@Args("id") id: string) { // query with an argument
return this.usersService.findOne(id);
}
@Mutation(() => User) // a mutation: creates a user
createUser(@Args("input") input: CreateUserInput) {
return this.usersService.create(input);
}
}
Resolvers (kama controllers, lakini kwa GraphQL) zinafafanua @Query na @Mutation handlers, zikikabidhi kazi kwa services kupitia DI — mitindo ileile kama REST controllers.
@ResolveField(() => [Post]) // resolve User.posts on demand
posts(@Parent() user: User) {
return this.postsService.findByUser(user.id);
}
// ⚠️ for lists, this can cause N+1 queries → use DataLoader to BATCH them
@ResolveField inatatua related/nested fields kwa uvivu (lazily) — lakini kwa lists, hii ina hatari ya tatizo la N+1 query, linalotatuliwa kwa DataLoader batching.
GraphQL: clients request EXACTLY the fields they need (no over/under-fetching),
one endpoint, strongly typed, great for complex/nested data & varied clients
REST: simpler, better HTTP caching, well-understood — fine for straightforward APIs
→ Choose based on needs, not hype. NestJS supports both equally well.
Uungaji mkono wa daraja la kwanza wa GraphQL wa NestJS ni wa thamani kwa sababu unaleta faida za GraphQL — wateja kupata data wanayohitaji haswa (kuondoa over- na under-fetching), endpoint moja yenye strong typing, na ushughulikiaji bora wa data tata/nested — ndani ya muundo unaojulikana, uliopangwa wa NestJS.
Kuielewa ni muhimu kwa kujenga API za kisasa, hasa mtindo wa code-first wa kawaida (kufafanua schema kwa TypeScript classes na @ObjectType/@Field/@Resolver decorators, huku schema ikizalishwa kiotomatiki na kuwekwa katika usawazishaji) ambao unalingana na architecture ya decorator/DI ya NestJS kwa asili — resolvers zinafanya kazi kama controllers tu, zikikabidhi kazi kwa services zilizoingizwa.
Kujua jinsi ya kufafanua types, queries, mutations, na resolved fields, na kufahamu tatizo la N+1 query (na DataLoader kama suluhisho) kwa nested data, ni maarifa muhimu ya kiwango cha senior.
Muhimu vivyo hivyo ni kuelewa trade-offs za GraphQL dhidi ya REST ili kuchagua njia sahihi kwa mradi husika (GraphQL kwa mahitaji ya data yanayonyumbulika, tata, ya multi-client; REST kwa API rahisi zenye HTTP caching imara).
GraphQL ni paradaimu kuu ya API, na ujumuishaji safi wa NestJS unaifanya kuwa uwezo muhimu, unaofaa mara kwa mara kwa kujenga back-ends zinazonyumbulika na zenye ufanisi.