Interacting with Metamask web3.js

Question

I am facing a problem when I am creating a contract on my local ethereum blockchain. I have a basic contract to register a doc on blockchain.
So, when a run my contract in truffle console I can call all my functions perfectly, but, when I create a webpage with a front end interface, I can't open metamask to pay a fee.
My contract has basicly 2 functions: addDoc and FindDoc. I did a test creating a transaction using remix website and it worked normal. At my page, I still can call a findDoc and get answer with the correct informations, but when I try creating a transaction and pay a fee, the metamask doesn't show me.

My project is just 4 files:

index.html
app.js
notaryWebApp.js
sha256

The codes can be found here: https://github.com/ffelipesimoes/solidity/tree/master/webapp

The main interact with blockchain is notaryWebApp.js file:

var contract = undefined; var customProvider = undefined; var address = "0x6A4494ed32ce0Ab8004fbEAdac534916f88C8d3E"; var abi = undefined; function notary_init() { // Check if Web3 has been injected by the browser (Mist/MetaMask) if (typeof web3 !== 'undefined') { // Use existing gateway window.web3 = new Web3(web3.currentProvider); } else { alert("No Ethereum interface injected into browser. Read-only access"); } //contract abi abi = [...] contract = new web3.eth.Contract(abi, address); }; //sends a hash to the blockchain function notary_send(hash, callback) { web3.eth.getAccounts(function (error, accounts) { contract.methods.addDocHash(hash).send({ from: accounts[0] }, function (error, tx) { if (error) callback(error, null); else callback(null, tx); }); }); }; //looks up a hash on the blockchain function notary_find(hash, callback) { contract.methods.findDocHash(hash).call(function (error, result) { if (error) callback(error, null); else { let resultObj = { mineTime: new Date(result[0] * 1000), blockNumber: result[1] } callback(null, resultObj); } }); };

since now, thank you all!

William Chong · Accepted Answer · 2020-02-17 09:59:07Z

2

You need to use window.ethereum and ethereum.enable() as described here, this is due to the privacy mode introduced in MetaMask recently.

In your case, call await window.ethereum.enable() before notary_init(), and init the web3 instance with window.ethereum instead of currentProvider.

answered Feb 17, 2020 at 9:59

William Chong

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3 Comments

Felipe Simões Over a year ago

Hey bud, thanks so much, your tip helped me so much. I did like this: I add the follow lines: <br> ethereum.enable() .then(function (accounts) { // You now have an array of accounts! // Currently only ever one: // ['0xFDEa65C8e26263F6d9A1B5de9555D2931A33b825'] }) .catch(function (error) { // Handle error. Likely the user rejected the login console.error(error) })

William Chong Over a year ago

You might want to add your working code in your original question, other people can then refer to your code if they have similar problem in the future. Also please accept my answer if it does help.

Felipe Simões Over a year ago

Hi, I did do, you can see above. Thanks for advice.

Felipe Simões · Accepted Answer · 2020-02-18 02:48:42Z

thnks so much. Worked that way:

function notary_init() { // Check if Web3 has been injected by the browser (Mist/MetaMask) if (typeof web3 !== 'undefined') { // Use existing gateway window.web3 = new Web3(web3.currentProvider); } else { alert("No Ethereum interface injected into browser. Read-only access"); } ethereum.enable() .then(function (accounts) { // You now have an array of accounts! // Currently only ever one: // ['0xFDEa65C8e26263F6d9A1B5de9555D2931A33b825'] }) .catch(function (error) { // Handle error. Likely the user rejected the login console.error(error) }) //contract abi abi =[...] contract = new web3.eth.Contract(abi, address); };

Edu Dhruv · Accepted Answer · 2020-02-17 09:33:56Z

Prefer using direct connection interface and predesigned scripts to solve this problem. You could find a package named Blockchain itself in pypi this could solve your problems and make sure that you are on the right folder ad=nd address

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