Decentralized Programmer: Part 2 Truffle
In this tutorial you will learn about Truffle. Truffle is must-have tool for an Ethereum programmer. It serves several purposes:
- development environment
- testing framework
- deployment pipeline
Installation
$ npm install -g truffle
Usage:
In terminal open a folder that you want to use for working on your solidity project and type:
truffle init
Here is what you will see:
Downloading...
Unpacking...
Setting up...
Unbox successful. Sweet!
Commands:
Compile: truffle compile
Migrate: truffle migrate
Test contracts: truffle test
If you check the contents of the folder you will see the following new items there:
- contracts/: Directory for Solidity contracts
- migrations/: Directory for scriptable deployment files
- test/: Directory for test files for testing your application and contracts
- truffle.js: Truffle configuration file
- truffle-config.js: Truffle configuration file
You can use following commands with Truffle.
- Compile: truffle compile
- Migrate: truffle migrate
- Test contracts: truffle test
Type the truffle compile in the terminal:
truffle compile
Compiling ./contracts/Migrations.sol...
Compilation warnings encountered:
/Users/jc_admin/Documents/GitHub/smart-contracts/TruffleFun/contracts/Migrations.sol:11:3: Warning: Defining constructors as functions with the same name as the contract is deprecated. Use "constructor(...) { ... }" instead.
function Migrations() public {
^ (Relevant source part starts here and spans across multiple lines).
Writing artifacts to ./build/contracts
What happened here? Truffle tried to compile your code, checking it for correct syntax during the process. You received a following warning:
Warning: Defining constructors as functions with the same name as the contract is deprecated. Use "constructor(...) { ... }"
Open a contracts/migration.sol in any text editor. You should be able to see following:
pragma solidity ^0.4.17;
contract Migrations {
address public owner;
uint public last_completed_migration;
modifier restricted() {
if (msg.sender == owner) _;
}
function Migrations() public {
owner = msg.sender;
}
function setCompleted(uint completed) public restricted {
last_completed_migration = completed;
}
function upgrade(address new_address) public restricted {
Migrations upgraded = Migrations(new_address);
upgraded.setCompleted(last_completed_migration);
}
}
Our suspect is a Migrations function, in the newest version of Solidity we should use constructor(). Go ahead and make a change and replace Migrations() with constructor():
pragma solidity ^0.4.17;
contract Migrations {
//code removed for clarity
function constructor() {
owner = msg.sender;
}
//code removed for clarity
Run the truffle compile again.
truffle compile
Compiling ./contracts/Migrations.sol...
Writing artifacts to ./build/contracts
This time your code executed without any warning!
Good job! You learn basics about Truffle, very powerful framework for working with Ethereum. You also found and correct a warning, that's a very important step in debugging your software.
If you want to learn more about Truffle visit the following page: http://truffleframework.com/docs/