https://github.com/thanhnguyennguyen/smart-contract-practice

Practicing with smart contract and Ethereum network using solidity
https://github.com/thanhnguyennguyen/smart-contract-practice

blockchain blockchain-demos erc20 erc20-tokens ethereum-contract ethereum-dapp nguyennguyen smartcontract-dapp smartcontracts thanhnguyennguyen

Last synced: 26 days ago
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Practicing with smart contract and Ethereum network using solidity

• Host: GitHub
• URL: https://github.com/thanhnguyennguyen/smart-contract-practice
• Owner: thanhnguyennguyen
• Created: 2018-06-10T15:32:04.000Z (over 7 years ago)
• Default Branch: master
• Last Pushed: 2023-03-02T01:47:34.000Z (over 2 years ago)
• Last Synced: 2025-07-30T16:21:13.300Z (3 months ago)
• Topics: blockchain, blockchain-demos, erc20, erc20-tokens, ethereum-contract, ethereum-dapp, nguyennguyen, smartcontract-dapp, smartcontracts, thanhnguyennguyen
• Language: JavaScript
• Size: 4.44 MB
• Stars: 9
• Watchers: 1
• Forks: 0
• Open Issues: 3
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

          


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# [![Deploy to Docker Cloud](https://files.cloud.docker.com/images/deploy-to-dockercloud.svg)](https://cloud.docker.com/stack/deploy/?repo=https://github.com/thanhnguyennguyen/smart-contract-practice/)

# Smart Contract practices

# Copyright © 2018 Nguyen Nguyen

# Please never write code without tests

## Lottery game

### Designs can be found here

https://github.com/thanhnguyennguyen/smart-contract-practice/tree/master/contracts/lottery/design

### Contract  url

https://rinkeby.etherscan.io/address/0xa0a5566cb16c16384f3b7b3a3a67cbbe0bf2f137

# Solidity basic knowledge

## Solidity data type

### ![Solidity data type 1](https://i.imgur.com/2P3XeQR.png)

### ![Solidity data type 2](https://i.imgur.com/majsyDN.png)

### ![Solidity data type 3](https://i.imgur.com/Yy9WIXI.png)

### ![Solidity data type 4](https://i.imgur.com/eL8TkKa.png)

## Memory and storage ![data-location](https://i.imgur.com/7H21p1E.jpg)

## Array in Solidity

### avoid nested array ![Solidity note 1](https://i.imgur.com/OkIIVRb.png)

### static and dynamic array ![dynamic-static](https://i.imgur.com/VohKPct.jpg)

### Not allowed ![not-allowed](https://i.imgur.com/UKJ8uOM.jpg)

### bytes and string are special arrays

bytes32 data; (~ byte[32] data )

bytes data (~ byte[] data )

String vss bytes ![string-vs-bytes](https://i.imgur.com/wr8vKTM.jpg)

## Functions

![function](https://i.imgur.com/1536CLf.jpg)

### Function visibilities and modifier ![func-visibilities](https://i.imgur.com/alCH2ma.jpg)

### Return multiple values ![func-return-multiple-values](https://i.imgur.com/OxoTTjh.jpg)

### To assign results from multiple returns function to variable, we use tupple ![tupple](https://i.imgur.com/xNsx5MU.jpg)

### Function overloading ![func-overloading](https://i.imgur.com/rR5LKdh.jpg)

Constructor overloading is not supported

## Variable initialization

Variables initialized to defaults at the beginning of functions

![variable-initialization](https://i.imgur.com/psByqb9.jpg)

## Mapping

### Difference between mapping and hashtable (of java) or object (of javascript) ![](https://i.imgur.com/1I1oYbCg.jpg)

### Mapping is defined as state , storage only, not allowed in function

## Enum and struct are not a part of ABI definition, not available for external function call

## Global variable: 

![global-var](https://i.imgur.com/svqPNGK.jpg)

### ![Solidity global variable 1](https://i.imgur.com/XWEcnzk.png)

### Difference between msg.sender and tx.origin ![msg-sender-vs-tx-origin](https://i.imgur.com/KfxiPbe.jpg)

## Error handling in Solidity

### No try-catch in  Solidity

### What happen if an exception is thrown

![exception](https://i.imgur.com/nGaxVnb.jpg)

### Check and handle exception ![handle-exception](https://i.imgur.com/qTfnym5g.jpg)

![](https://i.imgur.com/i1c8NBy.jpg)

## OOP Support

No keyword *abstract contract*, function declared but no body provided. That class can not be deployed

### Inheritance: multiple inheritance is supported

### Polimorphism 

### Overloading (except constructor)

## Interface and abstract contract

![difference-interface-abstrct-contract](https://i.imgur.com/ADqHHyr.jpg)

to implement an interface, use keywork *is*, similar for extending abstract contract

## Events and Logs

### Events are part of ABI definition

### Only indexed event arguments  can be used in Filter, maximum 3 indices are allowed

![event](https://i.imgur.com/rFD6sC8.jpg)

## Contract design patterns

### Contract destruction ![contract-destruction](https://i.imgur.com/DT2hfD0.jpg)

#### Sending tracsaction to dead contract: fail

#### ALl fund send to dead contract will be lost

### Factory contract

### Name registry pattern

Using a registry Contract to manage all contracts, then using contract name to access instance of a particular contract

### Mapping iterator pattern

#### Use another array to keep keys ![mapping-itorator-pattern](https://i.imgur.com/FZPwB1Tg.jpg)

#### Storage cost goes up

#### Cost of iteration goes up

### Withdrawal pattern

#### Send vs transfer ![send-vs-transfer](https://i.imgur.com/wzaCgxO.jpg)

#### Withdrawal pattern ![withdrawal-pattern](https://i.imgur.com/0lYuucS.jpg)

![](https://i.imgur.com/m5wyFD1.jpg)

# ERC-20 specification: 6 functions, 2 events

## ![ERC-20](https://i.imgur.com/jkLhW5G.jpg)

## ![ERC-20-2](https://i.imgur.com/IKnmPjT.jpg)

## ![ERC-20-3](https://i.imgur.com/ZPgaJcO.jpg)

## ![ERC-20-4](https://i.imgur.com/nJ34JFzg.jpg)

https://github.com/thanhnguyennguyen/ERC20-token

# web3 knowledge

## Send and Call

### ![Send-vs-call](https://i.imgur.com/m3ji3et.jpg)

## Filter object: web3.eth.filter

### ![filter](https://i.imgur.com/sFdgMLV.jpg)

### Event vs filter ![event-vs-filter](https://i.imgur.com/sb1RVbI.jpg)