Solidity Basics

Data Types

Arrays

uint[5] arr;// similar to std::array
uint[] vec;// similar to std::vector

uint newLength = vec.push(); // similar to .push_back()
vec.length; // similar to .size()

Mappings / Dictionary

mapping(K => V) map; // similar to std::map<K, V>

delete map[k]; // delete a specific key, similar to .erase()
delete map; // .clear()
//

Address

address 的本质是一个 20 byte 的值，指向一个 Ethereum Address. 如果额外添加关键词 payable 则表示这个 address 可以进行交易（自动拥有 transfer() 和 send() 方法）

Contract

Contract 的生态位

实际上我认为在设计代码架构的时候，还是应该将 Contract 视为 Class 进行处理. 不仅从逻辑上来说不叫相近，实现上也比较相近。

Important GLOBAL Variables

我们主要认识一下 msg 全局变量，msg 就是当前 contract 收到的消息，包含发送者、发送的金额等信息。

/* msg - Current message received by the contract */
msg.sender; // address of the sender
msg.value; // amount of ETH sent (in `wei`). Should be marked as [payable]
msg.data; // bytes, complete call data
msg.gas; // remaining gas

/* tx - this transaction */
tx.origin; // address of the sender of the transaction.
tx.gasprice; // Gas price

/* block - this block */
block.timestamp;
block.number;

Function Modifiers

Grammar to Define a Function

// function [NAME]([ARGUMENTS])
//      [VISIBILITY] [PAYABLE?] returns ([RETURN TYPE] [RETURN NAME]) {
// }
function someFunction(uint amount) public payable returns (uint remaining) {
    // do something here......
}

Function Visibility	Explanation
`public`	All other functions/contracts (including internal or external) can call this function
`private`	Only this contract can call this function
`external`	Can only be called from externally. If an internal one want to call, have to use `this` keyword
`internal`	Can only be called from internally.

payable: this function can receive & send ETH.