# Referensi Cepat GraphQL

*Schema, query, mutation, tipe, fragment*

> Source: GraphQL Documentation (graphql.org) · MIT

## Definisi Schema

### Root Schema

```
schema {
  query: Query
  mutation: Mutation
}
```

### Object Type

```
type User {
  id: ID!
  name: String!
  email: String
}
```

## Query

### Query Dasar

```
query {
  user(id: "1") {
    name
    email
  }
}
```

### Query Bernama dengan Alias

```
query GetUsers {
  admin: user(role: ADMIN) { name }
  guest: user(role: GUEST) { name }
}
```

## Mutation

### Mutation Dasar

```
mutation {
  createUser(input: { name: "Alice" }) {
    id
    name
  }
}
```

### Tipe Input

```
input CreateUserInput {
  name: String!
  email: String
}
```

## Subscription

### Subscription Dasar

```
subscription {
  messageAdded(channel: "general") {
    text
    sender { name }
  }
}
```

### Ringkasan

| Command | Description |
|---------|-------------|
| `subscription` | Data real-time via WebSocket |
| `Server push` | Server mengirim pembaruan ke client |
| `Single field` | Hanya satu root field per subscription |

## Tipe

### Scalar Type

| Command | Description |
|---------|-------------|
| `Int` | Integer 32-bit bertanda |
| `Float` | Bilangan pecahan presisi ganda |
| `String` | Urutan karakter UTF-8 |
| `Boolean` | true atau false |
| `ID` | Identifier unik (diserialisasi sebagai String) |

### Modifier Tipe

| Command | Description |
|---------|-------------|
| `String` | String nullable |
| `String!` | String non-null |
| `[String]` | List nullable berisi string nullable |
| `[String!]!` | List non-null berisi string non-null |

### Enum & Union

```
enum Role { ADMIN USER GUEST }
union SearchResult = User | Post
interface Node { id: ID! }
```

## Argumen & Variabel

### Variabel

```
query GetUser($id: ID!) {
  user(id: $id) {
    name
  }
}
# Variables: { "id": "123" }
```

### Nilai Default

```
query GetUsers($limit: Int = 10) {
  users(limit: $limit) { name }
}
```

## Fragment

### Fragment Bernama

```
fragment UserFields on User {
  id
  name
  email
}
```

### Menggunakan Fragment

```
query {
  user(id: "1") { ...UserFields }
  admin: user(id: "2") { ...UserFields }
}
```

### Inline Fragment

```
query {
  search(text: "a") {
    ... on User { name }
    ... on Post { title }
  }
}
```

## Directive

### Directive Bawaan

| Command | Description |
|---------|-------------|
| `@include(if: Boolean!)` | Sertakan field hanya jika kondisi benar |
| `@skip(if: Boolean!)` | Lewati field jika kondisi benar |
| `@deprecated(reason: String)` | Tandai field sebagai deprecated |

### Contoh Penggunaan

```
query GetUser($withEmail: Boolean!) {
  user(id: "1") {
    name
    email @include(if: $withEmail)
  }
}
```

## Introspection

### Introspection Tipe

```
query {
  __type(name: "User") {
    name
    fields { name type { name } }
  }
}
```

### Introspection Schema

```
query {
  __schema {
    types { name kind }
    queryType { name }
  }
}
```

### Field Introspection

| Command | Description |
|---------|-------------|
| `__schema` | Query tipe dan directive dari schema |
| `__type(name:)` | Query tipe tertentu berdasarkan nama |
| `__typename` | Mengembalikan nama tipe dari objek mana pun |

## Pola Umum

### Pagination (gaya Relay)

```
query {
  users(first: 10, after: "cursor") {
    edges { node { name } cursor }
    pageInfo { hasNextPage }
  }
}
```

### Penanganan Error

```
{
  "data": { "user": null },
  "errors": [{ "message": "Not found",
    "path": ["user"] }]
}
```

### Praktik Terbaik

| Command | Description |
|---------|-------------|
| `Beri nama operasi` | Selalu beri nama query dan mutation |
| `Gunakan variabel` | Jangan interpolasi nilai langsung ke query |
| `Minta field yang dibutuhkan` | Hindari over-fetching dengan seleksi yang tepat |
| `Gunakan fragment` | Bagikan kumpulan field antar query |