{"id":1742,"date":"2018-01-04T02:16:18","date_gmt":"2018-01-04T02:16:18","guid":{"rendered":"http:\/\/www.talkcrypto.org\/blog\/?p=1742"},"modified":"2018-01-08T00:38:35","modified_gmt":"2018-01-08T00:38:35","slug":"hello-world-ethereum-smart-contract","status":"publish","type":"post","link":"https:\/\/www.talkcrypto.org\/blog\/2018\/01\/04\/hello-world-ethereum-smart-contract\/","title":{"rendered":"Hello World Ethereum Smart Contract"},"content":{"rendered":"

Introduction<\/h3>\n

There are lots of simple Ethereum Hello World tutorials around to cater for everyone’s level. This tutorial builds on a 2016 version by Karl Floersh and attempts to keep things very simple. All that is required to be installed is Meta Mask which is currently a Chrome only plugin and is essentially an Ethereum light client browser plugin.<\/p>\n

More formally:<\/p>\n

“MetaMask is a bridge that allows you to visit the distributed web of tomorrow in your browser today. It allows you to run Ethereum dApps right in your browser without running a full Ethereum node.<\/em>“<\/p><\/blockquote>\n

Outcome<\/h3>\n

To deploy a hello world smart contract on the Ethereum network. Here is the code. It’s 1 contract consisting of 1 function and 1 event.<\/p>\n

contract HelloWorld {  \r\n    event log_string(bytes32 log); \/\/ Event\r\n\r\n    function () { \/\/ Fallback Function\r\n        log_string(\"Hello World!\");\r\n    }\r\n}\r\n<\/code><\/pre>\n
This guide should only take about 10 minutes to follow.<\/p>\n
Step 1: Install MetaMask<\/h3>\n
In Chrome, search for MetaMask and install it as a plugin. Then create an account and change the network to Ropsten. This is the test network.<\/p>\n
\"\"<\/p>\n
In order to get some test ether, click “BUY” and click “Ropsten test Faucet”.<\/p>\n
\"\"<\/p>\n
This will take you to https:\/\/faucet.metamask.io\/ where you can “request 1 ether from faucet”.<\/p>\n
Step 2: The Hello World code<\/h3>\n
Once you have MetaMask installed and managed to get some test ether, the next step is to compile the hello world code provided. Let’s understand the code first:<\/p>\n
contract HelloWorld {  \r\n    event log_string(bytes32 log); \/\/ Event\r\n\r\n    function () { \/\/ Fallback Function\r\n        log_string(\"Hello World!\");\r\n    }\r\n}<\/code><\/pre>\n
The first line declares a contract called HelloWorld. Next, an event is defined and accepts 1 argument of type bytes32. A function is then declared that invokes the event.<\/p>\n
For more info about events check out:<\/p>\n
https:\/\/media.consensys.net\/technical-introduction-to-events-and-logs-in-ethereum-a074d65dd61e
\nhttps:\/\/ethereum.stackexchange.com\/questions\/11228\/what-is-an-event
\nhttp:\/\/solidity.readthedocs.io\/en\/develop\/contracts.html#events<\/p>\n
Step 3: Compile and deploy the code<\/h3>\n
We will use the very popular online IDE (Integrated Development Environment) called Remix at http:\/\/remix.ethereum.org\/. Copy and paste the code in and click Run > Create<\/p>\n
\"\"<\/p>\n
A MetaMask notification will then appear. Click Submit to deploy the contract to the Ropsten blockchain.<\/p>\n
\"\"<\/p>\n
Step 4: View the deployed contract<\/h3>\n
Open MetaMask again and wait a few minutes for the contact to be deployed. Then click on it to open up the contract in Etherscan.<\/p>\n
\"\"<\/p>\n
This is what it should look like: https:\/\/ropsten.etherscan.io\/tx\/0xa142914ac224047fbf39a3b2ed92a68bc24fd301466d059fbe0e7810bdc8e5e9<\/p>\n
Congratulations. You have just deployed a very simple Hello World smart contract.<\/p>\n
Step 5: Invoke the contract<\/h3>\n
The contract is now alive on the Ethereum blockchain. The final question is how to we interact with it or trigger it.<\/p>\n
\"\"<\/p>\n
This is where we go back to MetaMask and send a transaction to the contract. First get the contract address. Look for the To field in the original contract deployed link at https:\/\/ropsten.etherscan.io\/tx\/0xa142914ac224047fbf39a3b2ed92a68bc24fd301466d059fbe0e7810bdc8e5e9<\/p>\n
\"\"<\/p>\n
In my case it is: 0xfd3811943d7e924607a2443465bc5deeb5847e14<\/p>\n
In MetaMask, click send and use the contract address as the Recipient Address. Leave the other fields as is and click Next.<\/p>\n
\"\"<\/p>\n
Again, leave all the default values as is and click Submit.<\/p>\n
\"\"<\/p>\n
Wait a few minutes for the transaction to go through and then check the Event Log of the transaction.<\/p>\n
\"\"<\/p>\n
https:\/\/ropsten.etherscan.io\/tx\/0x6b7f88e9590ec5af87133394d1301bbe4df736a66aff9c9519605f6a9dc4b0a7#eventlog<\/p>\n
\"\"<\/p>\n
The data field will be in hexidecimal. Change this to text and it should read “Hello World”!<\/p>\n
\"\"<\/p>\n
Summary<\/h3>\n
There are so many ways to deploy a smart contract. This guide used an online development environment in conjunction with a Chrome plugin called MetaMask to deploy a simple Hello World smart contract to the Ethereum testnet blockchain.<\/p>\n
The idea was to get up and going quickly with the minimum of moving parts.<\/p>\n
Ref:\u00a0https:\/\/karl.tech\/learning-solidity-part-1-deploy-a-contract\/<\/p>\n","protected":false},"excerpt":{"rendered":"
Introduction There are lots of simple Ethereum Hello World tutorials<\/p>\n","protected":false},"author":1,"featured_media":1756,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[4],"tags":[],"class_list":["post-1742","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-ethereum"],"featured_image_urls":{"full":["https:\/\/www.talkcrypto.org\/blog\/wp-content\/uploads\/2018\/01\/meta300.jpg",300,128,false],"thumbnail":["https:\/\/www.talkcrypto.org\/blog\/wp-content\/uploads\/2018\/01\/meta300-150x128.jpg",150,128,true],"medium":["https:\/\/www.talkcrypto.org\/blog\/wp-content\/uploads\/2018\/01\/meta300-300x128.jpg",300,128,true],"medium_large":["https:\/\/www.talkcrypto.org\/blog\/wp-content\/uploads\/2018\/01\/meta300.jpg",300,128,false],"large":["https:\/\/www.talkcrypto.org\/blog\/wp-content\/uploads\/2018\/01\/meta300.jpg",300,128,false],"1536x1536":["https:\/\/www.talkcrypto.org\/blog\/wp-content\/uploads\/2018\/01\/meta300.jpg",300,128,false],"2048x2048":["https:\/\/www.talkcrypto.org\/blog\/wp-content\/uploads\/2018\/01\/meta300.jpg",300,128,false],"chromenews-featured":["https:\/\/www.talkcrypto.org\/blog\/wp-content\/uploads\/2018\/01\/meta300.jpg",300,128,false],"chromenews-large":["https:\/\/www.talkcrypto.org\/blog\/wp-content\/uploads\/2018\/01\/meta300.jpg",300,128,false],"chromenews-medium":["https:\/\/www.talkcrypto.org\/blog\/wp-content\/uploads\/2018\/01\/meta300.jpg",300,128,false]},"author_info":{"info":["seandotau"]},"category_info":"Ethereum<\/a>","tag_info":"Ethereum","comment_count":"0","_links":{"self":[{"href":"https:\/\/www.talkcrypto.org\/blog\/wp-json\/wp\/v2\/posts\/1742","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.talkcrypto.org\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.talkcrypto.org\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.talkcrypto.org\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.talkcrypto.org\/blog\/wp-json\/wp\/v2\/comments?post=1742"}],"version-history":[{"count":3,"href":"https:\/\/www.talkcrypto.org\/blog\/wp-json\/wp\/v2\/posts\/1742\/revisions"}],"predecessor-version":[{"id":1759,"href":"https:\/\/www.talkcrypto.org\/blog\/wp-json\/wp\/v2\/posts\/1742\/revisions\/1759"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.talkcrypto.org\/blog\/wp-json\/wp\/v2\/media\/1756"}],"wp:attachment":[{"href":"https:\/\/www.talkcrypto.org\/blog\/wp-json\/wp\/v2\/media?parent=1742"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.talkcrypto.org\/blog\/wp-json\/wp\/v2\/categories?post=1742"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.talkcrypto.org\/blog\/wp-json\/wp\/v2\/tags?post=1742"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}