In my previous blog we have created our first Hello world
app using Remix Solidity IDE.
In this blog, I will go over how to use Visual Studio Code
to compile the Hello World contract and deploy the contract on a private chain
and Rinkeby chain. Please refer to my other related blogs for setting up Visual
Studio Code, Private Chain and connecting to Rinkeby Testnet.
Let’s start by opening Visual Studio Code and open a folder
in VS Code. If required create the folder. The folder is required because VS
code compiles the code and creates the abi and bytecode here.
Create a new file in this folder called HelloWorld.sol with
the below code:
pragma solidity ^0.4.11;
contract HelloWorld {
function
greet()
public constant returns (string) {
return "Hello World!";
}
}
Compile this smart contract by pressing F5 key. This creates
a bin folder with abi and bin (bytecode). Here are the contents of the abi and
bin file:
abi:
[{"constant":true,"inputs":[],"name":"greet","outputs":[{"name":"","type":"string"}],"payable":false,"type":"function"}]
bin(bytecode):
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
Here are the steps to be followed in the JavaScript console
to deploy the contract:
- Unlock the account so that Ether can be used for
gas
> personal.unlockAccount(eth.accounts[0],
"password")
true
In the above command I am using the first
account. If required you can specify any other account
- Define the abi & bytecode variables. Prefix
the bytecode with “0x”
var abi = [{ abi generated by the compiler
}]
var bytecode = “0x<bytecode generated by
compiler>”
> var contract = eth.contract(abi)
- Find the gas estimate for deploying the contract
eth.estimateGas({ data: bytecode} )
This gives the gas required to deploy the
contract. Currently it’s value is 138902. Specify this value in the next step
while creating an instance of this contract
- Now
create an instance of this contract.
> var instance = contract.new({
......
from:eth.accounts[0],
......
data:bytecode,
......
gas:138902}, function(err, contractInstance){
......
if(!err) {
......... if(!contractInstance.address) {
............ console.log("Tx Hash: " +
contractInstance.transactionHash) // The hash of the transaction
............ } else {
............ console.log("Address: " +
contractInstance.address) // the contract address
............ }
......... }
...... else {
......... console.log(err)
......... }
...... });
Tx Hash:
0x57228ccd8013aa17b134c3f76147a1c5a74f40f98c7bc352e484f42581e30355
undefined
> Address: 0x44408814564648d05d4cfcf12397151cfee0af52
The contract creation is an asynchronous
function. Once the contract is mined, the call back function returns the transaction
hash and address at which the contract is deployed.
- Wait till the contract is mined and address is
shown in the console
- Now invoke the greet function
> instance.greet()
"Hello World!"
With above steps we successfully deployed the contract onto
a private chain and invoked it. Here is the complete JavaScript console code:
personal.unlockAccount(eth.accounts[0], "password")
var abi = [{"constant":true,"inputs":[],"name":"greet","outputs":[{"name":"","type":"string"}],"payable":false,"type":"function"}]
var bytecode = "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"
var contract = eth.contract(abi)
var gas = eth.estimateGas({ data: bytecode} )
var instance = contract.new({
from:eth.accounts[0],
data:bytecode,
gas:gas}, function(err,
contractInstance){
if(!err) {
if(!contractInstance.address) {
console.log("Tx Hash: "
+ contractInstance.transactionHash) //
The hash of the transaction
} else {
console.log("Address: "
+ contractInstance.address) // the contract
address
}
}
else {
console.log(err)
}
});
//wait for the mining
to be completed
instance.greet()
I generally use Rinkeby during the UAT environment. Let’s
run the above script in the Rinkeby environment and check it. Please refer to
my other blog on how to connect to Rinkeby chain,
Setting
up Ethereum Rinkeby Testnet
I deployed the contract on Rinkeby network and here is the
screenshot of this contract:
