Copyright © 2018 Nguyen Nguyen Please never write code without tests Designs can be found here https://github.com/thanhnguyennguyen/smart-contract-practice/tree/master/contracts/lottery/design
https://rinkeby.etherscan.io/address/0xa0a5566cb16c16384f3b7b3a3a67cbbe0bf2f137
Memory and storage avoid nested array static and dynamic array Not allowed bytes and string are special arrays bytes32 data; (~ byte[32] data )
bytes data (~ byte[] data )
String vss bytes
Function visibilities and modifier Return multiple values To assign results from multiple returns function to variable, we use tupple Function overloading Constructor overloading is not supported
Variables initialized to defaults at the beginning of functions
Difference between mapping and hashtable (of java) or object (of javascript) 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
Difference between msg.sender and tx.origin Error handling in Solidity What happen if an exception is thrown
Check and handle exception
No keyword abstract contract , function declared but no body provided. That class can not be deployed
Inheritance: multiple inheritance is supported Overloading (except constructor) Interface and abstract contract is , similar for extending abstract contract
Events are part of ABI definition Only indexed event arguments can be used in Filter, maximum 3 indices are allowed
Contract destruction Sending tracsaction to dead contract: fail ALl fund send to dead contract will be lost Using a registry Contract to manage all contracts, then using contract name to access instance of a particular contract
Use another array to keep keys Cost of iteration goes up Send vs transfer Withdrawal pattern
ERC-20 specification: 6 functions, 2 events https://github.com/thanhnguyennguyen/ERC20-token
Filter object: web3.eth.filter Event vs filter 
