# Subgraph 超快速入门开发简要

**Published by:** [shaneson.eth](https://paragraph.com/@shaneson-eth/)
**Published on:** 2022-03-10
**URL:** https://paragraph.com/@shaneson-eth/subgraph

## Content

Subgraph其实非常简单。我这边大概就学了3个小时吧，就可以直接开发了。这里简单整理一下要点。介绍首先要知道它是做什么的。Subgraph是用来做链上数据索引的。熟悉区块链的底层的小伙伴肯定知道，假如要监听链上数据的事件/合约状态的话，我们一般是要写一个死循环，然后调用sdk来监听事件/合约，然后把数据存到数据库/处理。诸如此类的。但这很非常累。 我们很多的业务逻辑都是要监听链上数据然后进行分析的。基于此，Subgraph就诞生了。核心--- 链上数据索引（自定义的链上数据库）如果要快速入门subgraph，我觉得只需要理解到它是一个链上数据索引那么就没啥问题。直接可以看语法了。因为接下来的内容就和传统数据库的学习很相近了。create subgraph == 创建数据库创建图呢，有两种方法，法一：graph init \ --product subgraph-studio --from-contract <CONTRACT_ADDRESS> \ [--network <ETHEREUM_NETWORK>] \ [--abi <FILE>] \ <SUBGRAPH_SLUG> [<DIRECTORY>] 法二：graph init --studio <SUBGRAPH_SLUG> The is the ID of your subgraph in Subgraph Studio, it can be found on your subgraph details page. 修改subgraph配置 == 修改数据库配置 Subgraph的配置十分重要，但是方便的一点在于你几乎不用去做修改。graph-cli这个脚手架你可以基于你输入的合约地址，链的选择，项目名，合约名。去自动生成以下的文件。其中，最重要的应该是：eventHandlers，callHandlers和blockHandlers。这些是用来处理捕捉到事件/信号的时候用来处理数据的地方。 specVersion: 0.0.4 description: Gravatar for Ethereum repository: https://github.com/graphprotocol/example-subgraph schema: file: ./schema.graphql dataSources: - kind: ethereum/contract name: Gravity network: mainnet source: address: '0x2E645469f354BB4F5c8a05B3b30A929361cf77eC' abi: Gravity startBlock: 6175244 mapping: kind: ethereum/events apiVersion: 0.0.6 language: wasm/assemblyscript entities: - Gravatar abis: - name: Gravity file: ./abis/Gravity.json eventHandlers: - event: NewGravatar(uint256,address,string,string) handler: handleNewGravatar - event: UpdatedGravatar(uint256,address,string,string) handler: handleUpdatedGravatar callHandlers: - function: createGravatar(string,string) handler: handleCreateGravatar blockHandlers: - function: handleBlock - function: handleBlockWithCall filter: kind: call file: ./src/mapping.ts Entity Relation == 数据库设计 这一步几乎是最重要的。是对schema的设计，其实本质上可以理解成数据库设计。主要分为几种： 一对一关系 type Transaction @entity { id: ID! transactionReceipt: TransactionReceipt } type TransactionReceipt @entity { id: ID! transaction: Transaction } 一对多关系 type Token @entity { id: ID! } type TokenBalance @entity { id: ID! amount: Int! token: Token! } 多对多关系 type Organization @entity { id: ID! name: String! members: [User!]! } type User @entity { id: ID! name: String! organizations: [Organization!]! @derivedFrom(field: "members") } Data Source == Web开发中的 DAO层（或者数据输入) Emmm，这里本质就是当遇到callback的时候，要把什么数据写进graph上。这里就是具体逻辑具体分析了。我这里挑了abracadabra的一个MIM合约的Transfer函数做了监听，假如发生了Transfer，我就记下来。也是非常简单的。 import { Address, BigInt } from "@graphprotocol/graph-ts" import { MagicInternetMoney, Approval, OwnershipTransferred, Transfer } from "../generated/MagicInternetMoney/MagicInternetMoney" import { MintRecord, MagicInternetMoneyEntity} from "../generated/schema" export function handleTransfer(event: Transfer): void { const MagicInternetMoneyV1Instance = MagicInternetMoney.bind(event.address) const magicInternetMoneyID = event.address.toString() let magicInternetMoney = MagicInternetMoneyEntity.load(magicInternetMoneyID) let mintRecord = MintRecord.load(event.transaction.from.toHex()) // update MagicInternetMoney if (!magicInternetMoney) { magicInternetMoney = new MagicInternetMoneyEntity(magicInternetMoneyID) magicInternetMoney.decimals = MagicInternetMoneyV1Instance.decimals() magicInternetMoney.totalSupply = MagicInternetMoneyV1Instance.totalSupply() magicInternetMoney.save() } if (!mintRecord) { mintRecord = new MintRecord(event.transaction.from.toHex()) const _from = event.parameters[0].value.toAddress() const _to = event.parameters[1].value.toAddress() const _value = event.parameters[2].value.toBigInt() const _lastMint = MagicInternetMoneyV1Instance.lastMint() mintRecord.tokenReceiver = _from mintRecord.tokenReceiver = _to mintRecord.amount = _value mintRecord.time = _lastMint.value0 mintRecord.token = magicInternetMoney.id mintRecord.save() } } export function handleApproval(event: Approval): void {} export function handleOwnershipTransferred(event: OwnershipTransferred): void {} 编译 + 部署 两行命令就可以发布到子网/托管网络，实现数据监听了。非常方便。 graph codegen && graph build graph deploy --studio clink-demo

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