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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
  • Work with MIST
  • 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. Download Python: https://www.python.org/downloads/release/python-2712/

  2. .Net Packages https://www.microsoft.com/en-US/download/details.aspx?id=49982

https://www.microsoft.com/en-us/download/details.aspx?id=30653

  1. SSL https://slproweb.com/products/Win32OpenSSL.html

  2. and eventually you also need the Visual Studio, because of the C++ Compiler: https://www.visualstudio.com/vs/

After downloading the Visual Studio make sure to open one time a new c++ project.

  1. Install the Git-Bash as it comes with a mingw: https://git-scm.com/downloads

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

Ubuntu

  1. Install necessary packages:
sudo apt-get update && sudo apt-get upgrade
sudo apt-get install curl git vim build-essential
  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

npm install -g truffle

and then clone this repository

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

and run

bower install

which installs the angular components.

and then run

npm install

which installs the node components.

Additionally you need to have a geth node running (or the ethereumjs-testrpc), then you can simply:

truffle migrate

and

truffle build

or

truffle serve

which opens an HTTP Server on http://localhost:8080

Known Issues

Error when running truffle test/migrate

If something like this pops up:

dependency_path = source.resolve_dependency_path(import_path, dependency_path);

or

/usr/lib/node_modules/truffle/node_modules/truffle-compile/profiler.js:120
        if (ancestors.length > 0) {
                     ^

TypeError: Cannot read property 'length' of undefined
    at walk_from (/usr/lib/node_modules/truffle/node_modules/truffle-compile/profiler.js:120:22)

then try to install truffle 3.1.9:

npm install -g [email protected]

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.".

When you have installed Visual Studio, make sure you have opened a c++ project once.

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! The code throughout the course was written for SolC 3.5, the current version (at the time this Readme was written) is 0.4.8.

Any Solidity Program can be "forced" to use another compiler version (older one) by using as 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 0.4.8.

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.