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从应用程序中进行查询

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Learn how to query The Graph from your application.

Getting GraphQL Endpoints

During the development process, you will receive a GraphQL API endpoint at two different stages: one for testing in Subgraph Studio, and another for making queries to The Graph Network in production.

Subgraph Studio Endpoint

After deploying your subgraph to Subgraph Studio, you will receive an endpoint that looks like this:

https://api.studio.thegraph.com/query/<ID>/<SUBGRAPH_NAME>/<VERSION>

This endpoint is intended for testing purposes only and is rate-limited.

The Graph Network Endpoint

After publishing your subgraph to the network, you will receive an endpoint that looks like this: :

https://gateway.thegraph.com/api/<API_KEY>/subgraphs/id/<SUBGRAPH_ID>

This endpoint is intended for active use on the network. It allows you to use various GraphQL client libraries to query the subgraph and populate your application with indexed data.

Graph Client

The Graph is providing its own GraphQL client, graph-client that supports unique features such as:

Note: graph-client is integrated with other popular GraphQL clients such as Apollo and URQL, which are compatible with environments such as React, Angular, Node.js, and React Native. As a result, using graph-client will provide you with an enhanced experience for working with The Graph.

Fetch Data with Graph Client

Let’s look at how to fetch data from a subgraph with graph-client:

步骤1

Install The Graph Client CLI in your project:

yarn add -D @graphprotocol/client-cli# or, with NPM:npm install --save-dev @graphprotocol/client-cli

步骤2

Define your query in a .graphql file (or inlined in your .js or .ts file):

query ExampleQuery {  # this one is coming from compound-v2  markets(first: 7) {    borrowRate    cash    collateralFactor  }  #来自uniswap-v2的查询  pair(id: "0x00004ee988665cdda9a1080d5792cecd16dc1220") {    id    token0 {      id      symbol      name    }    token1 {      id      symbol      name    }  }}

步骤3

Create a configuration file (called .graphclientrc.yml) and point to your GraphQL endpoints provided by The Graph, for example:

# .graphclientrc.ymlsources:  - name: uniswapv2    handler:      graphql:        endpoint: https://gateway.thegraph.com/api/<API_KEY>/subgraphs/id/<SUBGRAPH_ID>  - name: compoundv2    handler:      graphql:        endpoint: https://gateway.thegraph.com/api/<API_KEY>/subgraphs/id/<SUBGRAPH_ID>documents:  - ./src/example-query.graphql

Step 4

Run the following The Graph Client CLI command to generate typed and ready to use JavaScript code:

graphclient build

Step 5

Update your .ts file to use the generated typed GraphQL documents:

import React, { useEffect } from 'react'// ...// we import types and typed-graphql document from the generated code (`..graphclient/`)import { ExampleQueryDocument, ExampleQueryQuery, execute } from '../.graphclient'function App() {  const [data, setData] = React.useState<ExampleQueryQuery>()  useEffect(() => {    execute(ExampleQueryDocument, {}).then((result) => {      setData(result?.data)    })  }, [setData])  return (    <div className="App">      <header className="App-header">        <img src={logo} className="App-logo" alt="logo" />        <p>Graph Client Example</p>        <fieldset>          {data && (            <form>              <label>Data</label>              <br />              <textarea value={JSON.stringify(data, null, 2)} readOnly rows={25} />            </form>          )}        </fieldset>      </header>    </div>  )}export default App

Important Note: graph-client is perfectly integrated with other GraphQL clients such as Apollo client, URQL, or React Query; you can find examples in the official repository⁠. However, if you choose to go with another client, keep in mind that you won’t be able to use Cross-chain Subgraph Handling or Automatic Pagination, which are core features for querying The Graph.

Apollo Client

Apollo client⁠ is a common GraphQL client on front-end ecosystems. It’s available for React, Angular, Vue, Ember, iOS, and Android.

Although it’s the heaviest client, it has many features to build advanced UI on top of GraphQL:

  • Advanced error handling
  • 分页
  • Data prefetching
  • Optimistic UI
  • Local state management

Fetch Data with Apollo Client

Let’s look at how to fetch data from a subgraph with Apollo client:

步骤1

Install @apollo/client and graphql:

npm install @apollo/client graphql

步骤2

Query the API with the following code:

import { ApolloClient, InMemoryCache, gql } from '@apollo/client'const APIURL = 'https://gateway.thegraph.com/api/<API_KEY>/subgraphs/id/<SUBGRAPH_ID>'const tokensQuery = `  query {    tokens {      id      tokenID      contentURI      metadataURI    }  }`const client = new ApolloClient({  uri: APIURL,  cache: new InMemoryCache(),})client  .query({    query: gql(tokensQuery),  })  .then((data) => console.log('Subgraph data: ', data))  .catch((err) => {    console.log('Error fetching data: ', err)  })

步骤3

To use variables, you can pass in a variables argument to the query:

const tokensQuery = `  query($first: Int, $orderBy: BigInt, $orderDirection: String) {    tokens(      first: $first, orderBy: $orderBy, orderDirection: $orderDirection    ) {      id      tokenID      contentURI      metadataURI    }  }`client  .query({    query: gql(tokensQuery),    variables: {      first: 10,      orderBy: 'createdAtTimestamp',      orderDirection: 'desc',    },  })  .then((data) => console.log('Subgraph data: ', data))  .catch((err) => {    console.log('Error fetching data: ', err)  })

URQL Overview

URQL⁠ is available within Node.js, React/Preact, Vue, and Svelte environments, with some more advanced features:

  • 灵活的缓存系统
  • 可扩展设计(使在它上面添加新功能变得容易)
  • 轻量级捆绑包(比 Apollo Client 小约5倍)
  • 支持文件上传和离线模式

Fetch data with URQL

Let’s look at how to fetch data from a subgraph with URQL:

步骤1

Install urql and graphql:

npm install urql graphql

步骤2

Query the API with the following code:

import { createClient } from 'urql'const APIURL = 'https://gateway.thegraph.com/api/<API_KEY>/subgraphs/id/<SUBGRAPH_ID>'const tokensQuery = `  query {    tokens {      id      tokenID      contentURI      metadataURI    }  }`const client = createClient({  url: APIURL,})const data = await client.query(tokensQuery).toPromise()
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