X'inhi schema ta' GraphQL? Spjega t-tipi scalar u object.

Question

IT Interview Practice · Accepted Answer

**Schema** hija l-kuntratt tipizzat ta' API GraphQL miktub f'SDL (Schema Definition Language). Tiddikjara kull tip, kull field, u r-**root types** speċjali — `Query` (qari), `Mutation` (kitba), u b'mod fakultattiv `Subscription` (live). Is-server jiċħad kwalunkwe request li ma taqbilx mas-schema.

## Tipi scalar kontra object

- **Scalar types** huma valuri leaf li jżommu data reali: dawk built-in huma `Int`, `Float`, `String`, `Boolean`, u `ID`. Tista' wkoll tiddefinixxi custom scalars bħal `DateTime`.
- **Object types** jiġbru l-fields flimkien. Il-fields tagħhom jistgħu jkunu scalars *jew* object types oħra, li huwa kif timmodella r-relazzjonijiet.

```graphql
scalar DateTime                # a custom scalar

type User {                    # an object type
  id: ID!                      # ! means non-null (always present)
  name: String!
  createdAt: DateTime!
  posts: [Post!]!              # a list of Post objects, non-null list of non-null items
}

type Post {
  id: ID!
  title: String!
  author: User!                # points back to User -> a relationship
}

type Query {                   # root type: the entry points for reads
  user(id: ID!): User          # a field with an argument; returns a User (nullable)
}
```

Il-`!` jimmarka **non-null**; `[Post!]!` huwa non-null list li l-items tiegħu huma non-null. L-arguments (`id: ID!`) iħallu field jiġi parametrizzat.

## Għaliex huwa importanti

Is-schema hija l-uniku single source of truth — tmexxi l-validazzjoni, id-docs awto-ġġenerati, u l-codegen tal-klijent. Li taqra `!` u t-tipi list b'mod korrett hija verifika komuni ta' screening għal junior, u d-deċiżjonijiet dwar in-nullability jiffurmaw kif il-klijenti jimmaniġġjaw l-errors.

Tipi scalar kontra object

Għaliex huwa importanti

Mistoqsijiet relatati