Final DApp

This is the final DApp you are going to develop in the Etheruem Class.

Scope

The scope of the DApp is to show the usage of Truffle,

• demonstrate how to work with the Ethereum Blockchain
• Web3
• Listen and react to specific events
• Write Test Cases
• Deploy the DApp using MetaMask or Truffle
• Work with Ganache, Go-Etheruem and other Blockchain Nodes
• Understand where Private Keys are located at
• Integrate Angular into Truffle

Install Instructions

Developing for Ethereum is sometimes frustrating, because things change at fast pace. If something does not work as described here, please:

1. try a google search as you are 100% not alone with your problem
2. inform the instructors of the course so they can correct the problem
3. if you have the time, it would be awesome if you'd make a pull-request here

Windows

1. Install NodeJS and the Node Package Manager (NPM) https://nodejs.org/en/download/

2. Install the windows-build-tools npm install -g windows-build-tools

Ubuntu

1. Install NodeJS and NPM

 curl -sL https://deb.nodesource.com/setup_6.x | sudo -E bash -
 sudo apt-get install -y nodejs
 sudo npm install -g express

Other Necessary Files

Download the Genesis File either from here or directly from the go-ethereum github page. It is advised to take it directly from the official github page, as it is probably more up to date.

Run the Project

On any OS you need Truffle 5, which is at the time of writing in Beta. The Project is optimized for Solidity 0.5.0

npm install -g truffle@beta

and then clone this repository

git clone https://github.com/tomw1808/truffle_eth_class1.git

and run

npm install

which installs the node components.

Additionally you need to have a geth/ganache node running (or the ethereumjs-testrpc):

npm install ganache-cli

and then start ganache-cli:

ganache-cli -b 3

then you can simply:

truffle migrate

and

npm start

which opens an HTTP Server on http://localhost:4200/

Known Issues

Error when installing truffle

Something like

... receive errors including "MSBUILD : error MSB3428: Could not load the Visual C++ component "VCBuild.exe".

or

... node_modules\truffle\node_modules\sha3\build\sha3.vcxproj(20,3): error MSB4019: The imported project "C:\Microsoft.Cpp.Default.props" was not found. Confirm that the path in the <Import> declaration is correct, and that the file exists on disk.".

Then try npm config set msvs_version 2015 --global and in addition you can try to install the ms-build tools:

npm install --global --production windows-build-tools

Geth Attach

https://www.udemy.com/ethereum-developer/learn/v4/questions/1846724

On Windows its simply possible to do a geth attach, but on MacOS it seems that you need to provide the actual ipc file. geth --datadir /media/user/sdcard/chaindata --ipcpath $HOME/.ethereum/geth.ipc console which is a problem posed here: http://ethereum.stackexchange.com/questions/4472/port-30303-error-in-mist-when-i-run-geth-with-a-different-datadir

Private Network

The way the private network is initialized changed in the past months and seems to keep changing. For better information on it, it is advised to directly see the correct instructions on: https://github.com/ethereum/go-ethereum

Usually it should work with:

geth init path/to/genesis.json --datadir=/path/to/some/folder

Solidity Compilation Errors/Warnings

Solidity is in active maintenance and things change all the time!

Any Solidity Program can be "made" to use another compiler version (older one) by defining it in the first line in your program pragma solidity ^0.4.0; for version 0.4.0, change it to whatever version you might need.

The code here is updated to work with solidity 0.5.0.

Contact

If you run into any problems, don't hesitate to contact us on the course-forum at any time. If you use the forum-search function, there is a high chance that you find the answer to your problem already.