Ethereum Development

· 356 words · 2 minute read

How to generate etheruem key pair 🔗

key generate

Ethereum Application Development 🔗

Enviriment 🔗

Ubuntu 16.04LTS server Geth 1.83 stable Nodejs 8.11.1 web3.js 0.20.1

eth-netstats 🔗

It look like there’re two part one is netstats(監控端),and another one is client(客戶端) https://kairen.github.io/2017/05/26/blockchain/geth-monitoring/

Web3.js 🔗

go-ethereum和parity支援web3.js :::warning 如果你要透過套件安裝web3.js 的library，要注意geth內的web3版本(web3.version)，之前使用1.X.X版本有問題，目前改為0.2X.X版 :::

可以由此查看web3.js版本0.20.1 API v0.2X.X

  • Upadate 2018/6/4 : web3.js 1.0.0 is more efficient

accounts.sign v.s eth.sign 🔗

There’s a little bit diff between accounts.sign & eth.sign, you can’t encode by one of the and decode by another one. That’s because they are encode with diff parameter. Web3.js : eth.sign() vs eth.accounts.sign() — producing different signatures?

Old way : eth.sign New way : accounts.sign(more ez to use it can recover without contract)

Geth 🔗

how to add account into geth? 🔗

Copy keyfile(File name begin with UTC…) into floder which call keystore in the local of geth.

What is an Ethereum keystore file? Keystore file

https://github.com/OSE-Lab/learning-blockchain/blob/master/ethereum/docker-geth-multi-nodes.md

Smart Contract-solidity 🔗

how to return whole struct? 🔗

You can not return struct cuz the length of interface, but there is a solution. You can return them with chunks sperate them to the peices like example downblow.

pragma solidity ^0.4.0;
contract Cloud2{
    struct Metadata{
        string fileName;
        address addr;
        bytes16 hashId;
        uint timestamp;
    }
    mapping(bytes16 => Metadata) public fileInfos;
    function setFile(string fileName, address addr,bytes16 hashId, uint timestamp) public returns(bytes16){
        fileInfos[hashId]=Metadata(fileName,addr,hashId,timestamp);
        return hashId;
    }
    function getFileWithHash(bytes16 hashId) public constant returns(string, address, uint) {
        return (fileInfos[hashId].fileName, fileInfos[hashId].addr, fileInfos[hashId].timestamp);
    }
}

How to call the method? 🔗

There are few way to call. If you need to change the value in contract you should pay the gas(send the trancation to call)

Contract Method

// Automatically determines the use of call or sendTransaction based on the method type
myContractInstance.myMethod(param1 [, param2, ...] [, transactionObject] [, defaultBlock] [, callback]);

// Explicitly calling this method
myContractInstance.myMethod.call(param1 [, param2, ...] [, transactionObject] [, defaultBlock] [, callback]);

// Explicitly sending a transaction to this method
myContractInstance.myMethod.sendTransaction(param1 [, param2, ...] [, transactionObject] [, callback]);

// Get the call data, so you can call the contract through some other means
// var myCallData = myContractInstance.myMethod.request(param1 [, param2, ...]);
var myCallData = myContractInstance.myMethod.getData(param1 [, param2, ...]);
// myCallData = '0x45ff3ff6000000000004545345345345..'

web3.js 0.2x.x

ethereum evm blockchain