How to call methods of Ethereum Smart-Contracts from WordPress with MetaMask, Web3 and Javascript (PART II)

This post is the continuation of the previous post:

• How to call methods of Ethereum Smart-Contracts from WordPress with MetaMask, Web3 and Javascript

Now we want to call the method “buy” and send some Ether in the transaction to buy tokens from our Ethereum Smart-contract (for MAAT tokens).

Then we must change the javascript code (to change the function to call and to send some Ether). See below the code:

<script src="http://rawgit.com/ethereum/web3.js/0.16.0/dist/web3.min.js"></script>
<script src="https://cdn.jsdelivr.net/npm/ethjs@0.3.0/dist/ethjs.min.js"></script>
<script>
window.addEventListener('load', function() {
 // Check if Web3 has been injected by the browser:
 if (typeof web3 !== 'undefined') {
 // You have a web3 browser! Continue below!
 startApp(web3);
 //alert("Web3");
 } else {
 //alert("No hay web3");
 // Warn the user that they need to get a web3 browser
 // Or install MetaMask, maybe with a nice graphic.
 }
})
const abi = [{
 "constant": false,
 "inputs": [
 ],
 "name": "buy",
 "outputs": [
 {
 "name": "success",
 "type": "bool"
 }
 ],
 "payable": true,
 "type": "function"
 }]
const contract_address = '0xf035755df96ad968a7ad52c968dbe86d52927f5b'
const etherValue = web3.toWei(10, 'ether');
var address = '0x91612055A68aD74A6e756615941Ac59e9220A940'
function startApp(web3) {
 //alert("entro");
 const eth = new Eth(web3.currentProvider)
 const token = eth.contract(abi).at(contract_address);
 listenForClicks(token,web3)
 //alert("llego");
}
function listenForClicks (miniToken, web3) {
 var button = document.querySelector('button.transferFunds')
 web3.eth.getAccounts(function(err, accounts) { console.log(accounts); address = accounts.toString(); })
 button.addEventListener('click', function() {
miniToken.buy( { from: address, value: '1000000000000000000' })
 .then(function (txHash) {
 console.log('Transaction sent')
 console.dir(txHash)
 waitForTxToBeMined(txHash)
 })
 .catch(console.error)
 })
}
async function waitForTxToBeMined (txHash) {
 let txReceipt
 while (!txReceipt) {
 try {
 txReceipt = await eth.getTransactionReceipt(txHash)
 } catch (err) {
 return indicateFailure(err)
 }
 }
 indicateSuccess()
}
</script>
<button class="transferFunds">Send Money!</button>

Now we can update the wordpress page and try pushing again the “button“.

MetaMask will be opened with 1 Ether to send to the method “buy” of the contract.

Once approved the transaction, will be visible in Etherscan with the MAAT token result for us.

That’s all! Very easy!

If you want to read the smart-contract source, is here (in the Ethereum Testnet)

By MrAddon