Resolvers ni nini? Eleza resolver chain na arguments zake.

Question

IT Interview Practice · Accepted Answer

**Resolver** ni function inayozalisha thamani kwa field moja katika schema. GraphQL hupitia query field kwa field na kuita resolver inayolingana kwa kila moja — mchakato huo ndio **resolver chain**.

## Arguments nne za resolver

Kila resolver hupokea `(parent, args, context, info)`:

- **parent** — thamani iliyorudishwa na resolver ya ngazi moja juu (mfano, object `User` unaposuluhisha `user.posts`).
- **args** — arguments za field kutoka kwa query (`{ id: "1" }`).
- **context** — object ya kila-ombi inayoshirikiwa na resolvers zote; hushikilia taarifa za auth, DB client, loaders.
- **info** — AST na maelezo ya utekelezaji (hutumika mara chache).

```js
const resolvers = {
  Query: {
    // top-level: parent is undefined; read args, use context for data access
    user: (_parent, args, ctx) => ctx.db.users.findById(args.id),
  },
  User: {
    // runs for EACH user; parent is the resolved user object
    posts: (parent, _args, ctx) => ctx.db.posts.findByAuthor(parent.id),
    // no resolver needed for 'name' -> the default resolver reads parent.name
  },
};
```

Ikiwa field haina resolver ya wazi, GraphQL hutumia **default resolver** inayosoma tu `parent[fieldName]`. Ndiyo sababu scalar fields kwenye object ya kawaida mara nyingi hazihitaji code.

## Kwa nini ni muhimu

Kuelewa kuwa resolvers hukimbia **kwa kila field, kutoka juu kwenda chini, zikifuata parent chain** kunafafanua jinsi data iliyofungamana inavyokusanywa na pia kwa nini nested resolvers za kawaida husababisha tatizo la N+1 — swali la ufuatiliaji la kawaida katika mahojiano.

Arguments nne za resolver

Kwa nini ni muhimu

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