add contract deployment page

pull/26459/head^2
Joe 2 years ago
parent 357825b2f4
commit 56f59978d6
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      src/pages/docs/interacting-with-geth/javascript-console_contracts.md

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---
title: JavaScript Console 2: Contracts
description: Instructions for working with contracts in the Javascript console.
---
The [Introduction to the Javascript console](src/pages/docs/interacting-with-geth/javascript-console.md) page outlined how a Javascript console can be attached to Geth to provide a more user-friendly interface to Ethereum than interacting directly with the JSON-RPC API. This page will describe how to deploy contracts and interact with contracts using the attached console. This page will assume the Javascript console is attached to a running Geth instance using IPC. Clef should be used to manage accounts.
## Deploying a contract
First we need a contract to deploy. We can use the well-known `Storage.sol` contract written in Solidity. The following Solidity code can be copied and pasted into a text editor and saved as `go-ethereum/storage-contract/Storage.sol`.
```Solidity
// SPDX License-Identifier: GPL 3.0
pragma solidity ^0.8.0;
contract Storage{
uint256 value = 5;
function set(uint256 number) public{
value = number;
}
function retrieve() public view returns (uint256){
return value;
}
}
```
The contract needs to be compiled before Geth can understand it. Compiling the contract creates an [Application Binary Interface](src/pages/docs/tools/abigen.md) and the contract bytecode. This requires a Solidity compiler (e.g. `solc`) to be installed on the local machine. Then, compile and save the ABI and bytecode to a new `build` subdirectory using the following terminal commands:
```sh
cd ~/go-ethereum/storage-contract
solc --bin Storage.sol -o build
solc --abi Storage.sol -o build
```
The outputs look as follows:
```sh
# build/Storage.bin
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
```
```json
# Storage.abi
[{"inputs":[],"name":"retrieve","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"stateMutability":"view","type":"function"},{"inputs":[{"internalType":"uint256","name":"number","type":"uint256"}],"name":"store","outputs":[],"stateMutability":"nonpayable","type":"function"}]
```
These are all the data required to deploy the contract using the Geth Javascript console. Open the Javascript console using `./geth attach geth.ipc`.
Now, for convenice we can store the abi and bytecode in variables in the console:
```js
var abi = [{"inputs":[],"name":"retrieve","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"stateMutability":"view","type":"function"},{"inputs":[{"internalType":"uint256","name":"number","type":"uint256"}],"name":"store","outputs":[],"stateMutability":"nonpayable","type":"function"}]
var bytecode = "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"
```
The ABI can be used to create an instance of the contract:
```js
var contract = eth.contract(abi)
```
This contract instance can then be deployed to the blockchain. This is done using `eth.sendTransaction`, passing the contract bytecode in the `data` field. For convenience we can create a transaction JSON object first, then pass it to `eth.sendTransaction` later. Let's use the first account in `eth.accounts` as the sender. The amount of gas to include can be determined using `eth.estimateGas`:
```js
var gas = eth.estimateGas({data: bytecode})
```
Note that each command that touches accounts will require approval in Clef unless a custom rule has been implemented.
```js
var tx = {'from': eth.accounts[0], data: bytecode, gas: gas}
var deployed_contract = contract.new(tx)
```
The transaction hash and deployment address can now been viewed in the console by entering the variable name (in this case `deployed_contract`):
```js
{
abi:[{
inputs: [],
name: "retrieve",
outputs: [{...}],
stateMutability: "view",
type: "function"
},{
inputs: [],
name: "store",
outputs: [{...}],
stateMutability: "nonpayable",
type: "function"
}],
address: "0x2d6505f8b1130a22a5998cd31788bf6c751247f",
transactionHash: "0x5040a8916b23b76696ea9eba5b072546e1112cc481995219081fc86f5b911bf3",
allEvents: function bound(),
retrieve: function bound(),
store: function bound()
}
```
Passing the transaction hash to `eth.getTransaction()` returns the deployment transaction details including the contract bytecode in the `input` field. To interact with the contract, create an instance by passing the deployment address to `contract.at` then call the methods.
```js
var instance = contract.at("0x2d6505f8b1130a22a5998cd31788bf6c751247f")
// store() alters the state and therefore requires sendTransaction()
contract.set.sendTransaction(42, {from: eth.accounts[0], gas: 1000000})
// retrieve does not alter state so it can be executed using call()
contract.retrieve().call()
>> 2
```
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