[Ethereum] Why setting balanceOf instead of just using public variable in ERC20 tokens

Architectureerc-20mappingsoliditytokens

Good day,

ERC20 specify the following 2 functions as its most important ones:

function balanceOf(address _owner) constant returns (uint256 balance){}
function transfer(address _to, uint256 _value) returns (bool success){}

But the balanceOf function is nothing more than a fancy way to access the info stored inside a simple mapping array.
Why not just set the balances mapping array to be public and be done with it?

mapping (address=>uint) public balanceOf;

I feel as if I'm missing something here.
As always, your help is appreciated.

Best Answer

The function just defines a way of accessing the mapping array and assumes that you haven't set its modifier to public.

In ether wallets they both seem to work in the same way so no real difference if you just need to see balances.

Related Solutions

[Ethereum] API to “Read Contract Information” to fetch stats of an ICO

Which version of web3 are you using?

Here is a working example with web3@^1.0.0-beta.34

const Web3 = require('web3');
contractAddress = '0xe7775a6e9bcf904eb39da2b68c5efb4f9360e08c';
provider = 'https://mainnet.infura.io';
const contractAbiJSON = '';//... The JSON abi

// Init
const web3 = new Web3(new web3.providers.HttpProvider(provider));

const contract = new web3.eth.Contract(contractAbiJSON, contractAddress);

contract.methods.totalSupply().call().then((totalSupply) => {
  console.log(totalSupply);
});

[Ethereum] This contract does not implement all functions and thus cannot be created

The problem is that totalSupply() implementation is missing. Seems like autogenerated getters do not count. So you need to explicitly create the function.

contract StandardToken is Token {
    uint256 _totalSupply;

    function totalSupply() constant returns (uint256 totalSupply) {
        totalSupply = _totalSupply;
    }
}

Best Answer

Related Solutions

[Ethereum] API to “Read Contract Information” to fetch stats of an ICO

[Ethereum] This contract does not implement all functions and thus cannot be created

Related Topic