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94 lines
2.7 KiB
Markdown
94 lines
2.7 KiB
Markdown
# Concepts
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GraphQL is data-centric. On the very top level it is built around three major concepts:
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**Schema**, **Query** and **Mutation**.
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You are expected to expresses your application as **Schema** (aka Type System) and expose it
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with single HTTP endpoint. Application clients (e.g. web or mobile clients) send **Queries**
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to this endpoint to request structured data and **Mutations** to perform changes.
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## Queries
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Queries are expressed in simple language that resembles JSON:
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```graphql
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{
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hero {
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name
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friends {
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name
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}
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}
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}
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```
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It was designed to mirror the structure of expected response:
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```json
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{
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"hero": {
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"name": "R2-D2",
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"friends": [
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{"name": "Luke Skywalker"},
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{"name": "Han Solo"},
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{"name": "Leia Organa"}
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]
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}
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}
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```
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**graphql-php** runtime parses Queries, makes sure that they are valid for given Type System
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and executes using data resolving tools provided by you as a part of integration.
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## Mutations
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Mutations use advanced features of the very same query language (like arguments and variables)
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and have only semantic difference from Queries:
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```graphql
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mutation CreateReviewForEpisode($ep: Episode!, $review: ReviewInput!) {
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createReview(episode: $ep, review: $review) {
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stars
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commentary
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}
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}
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```
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Variables `$ep` and `$review` are sent alongside with mutation. Full HTTP request might look like this:
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```json
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// POST /graphql-endpoint
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// Content-Type: application/javascript
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//
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{
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"query": "mutation CreateReviewForEpisode...",
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"variables": {
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"ep": "JEDI",
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"review": {
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"stars": 5,
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"commentary": "This is a great movie!"
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}
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}
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}
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```
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As you see variables may include complex objects and they will be correctly validated by
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**graphql-php** runtime.
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Another nice feature of GraphQL mutations is that they also hold the query for data to be
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returned after mutation. In our example mutation will return:
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```
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{
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"createReview": {
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"stars": 5,
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"commentary": "This is a great movie!"
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}
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}
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```
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# Type System
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Type system is a heart of GraphQL integration. That's where **graphql-php** comes into play.
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It provides following tools and primitives to describe your App as hierarchy of types:
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* Primitives to work with **objects** and **interfaces**
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* Primitives for defining **enumerations** and **unions**
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* Primitives for defining custom **scalar types**
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* Built-in scalar types: `ID`, `String`, `Int`, `Float`, `Boolean`
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* Built-in type modifiers: `ListOf` and `NonNull`
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# Further Reading
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To get deeper understanding of GraphQL concepts - [read the docs on official website](http://graphql.org/learn/)
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To get started with your own app - continue to next section ["Getting Started"](getting-started/) |