（32 小時最全課程）區(qū)塊鏈，智能合約 & 全棧 Web3 開發(fā)
# Full BlockChain Solidity Learning
## Chapter #1
### Calculate Transaction Fee
Transaction Fee = ( Block Base Fee Per Gas + MaxPriorityFee Per Gas ) \* Gas Used
- Base Fee: The minimum "gas price" to send your transaction
- 1 Eth = 1000000000 GWei = 1000000000000000000 Wei
### Consensus
Consensus is the mechanism used to agree on the state of a blockchain.
#### 1. Chain Selection Algorithm
#### 2. Sybil Resistance Mechanism
- Like PoW(Proof of Work) and PoS(Proof of Stake)
## Chapter #2
### First Contract in Remix
```sol
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.7;
// This is a smart contract
contract SimpleStorage {
// The basic types: boolean | unit | int | address | bytes
// unit: POSITIVE number only
bool hasFavoriteNumber = true;
uint favoriteNumber = 123;
string favoriteNumberInText = 'five';
bytes favoriteBytes = 'cat';
}
```
> Default Value
> `uint favoriteNumber; // 0`
### Function
```sol
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.7;
// Contract: 0xd9145CCE52D386f254917e481eB44e9943F39138
contract SimpleStorage {
uint256 favoriteNumber;
function store(uint256 _favoriteNumber) public {
favoriteNumber = _favoriteNumber;
}
// getter function of favoriteNumber
function retrieve() public view returns(uint256) {
return favoriteNumber;
}
}
```
> **Tips:**
>
> - Smart Contracts have addresses just like our wallet accounts do.
> - Any time you change something on-chain, including making a new contract, it happens in a transaction.(部署合約其實就是在發(fā)送一個交易；我們在區(qū)塊鏈上做任何事情，修改任何狀態(tài)，其實就是在發(fā)送一個交易)
> - `view, pure`: 標(biāo)記上后不會花費 gas，因為這意味著我們只會讀取這個合約的狀態(tài)（除非你在要花費 gas 的 store 函數(shù)中調(diào)用它）
> - `view and pure` functions disallow modification of state.(我們不可以在這個函數(shù)里修改任何狀態(tài))
#### Function Visibility Specifiers
- public: it creates `getter()` automatically.
- private: only visible in current contract.(此合約可見)
- external: only visible externally.(合約外部可見，合約外的賬戶可以調(diào)用這個函數(shù))
- internal(default visibility ): only visible internally.(合約內(nèi)部可見，這有這個合約或者繼承它的合約可以調(diào)取)
### Arrays and Structure
We want to store different people with different numbers here. So we are using `struct`.
```sol
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.7;
// Contract: 0xd9145CCE52D386f254917e481eB44e9943F39138
contract SimpleStorage {
uint256 public favoriteNumber;
// Instantiate a person
People public person = People({favoriteNumber: 12, name: 'Logic'});
struct People {
uint256 favoriteNumber;
string name;
}
function store(uint256 _favoriteNumber) public {
favoriteNumber = _favoriteNumber;
}
// getter function of favoriteNumber
function retrieve() public view returns(uint256) {
return favoriteNumber;
}
}
```
We are storing the structures as an array here
```sol
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.7;
// Contract: 0xd9145CCE52D386f254917e481eB44e9943F39138
contract SimpleStorage {
uint256 public favoriteNumber;
struct People {
uint256 favoriteNumber;
string name;
}
// 這里用people數(shù)組來存儲多個`struct`的實例`People`
People[] public people;
// Add `people` function
function addPerson(string memory _name, uint256 _favoriteNumber) public {
People memory newPerson = People({favoriteNumber: _favoriteNumber, name: _name});
// People memory newPerson = People(_favoriteNumber, _name);
people.push(newPerson);
}
function store(uint256 _favoriteNumber) public {
favoriteNumber = _favoriteNumber;
}
// getter function of favoriteNumber
function retrieve() public view returns(uint256) {
return favoriteNumber;
}
}
```
> - 創(chuàng)建了 people 數(shù)組，編制后會有一個`people`的按鈕，這里可以輸入`index`來找到對應(yīng)的 structure；
> - 同時，這里還寫了`addPerson`函數(shù)來添加 structure 到 array 中；
> - `memory`是一種 solidity 的存儲方式，這里表示的是臨時存儲，函數(shù)執(zhí)行完畢后數(shù)據(jù)會被清除。
### Memory, Storage and Calldata
EVM can access and store information in six places:
1. Stack
2. Memory: 可以被修改的臨時變量
3. Storage: 可以被修改的永久變量
4. Calldata: 不能被修改的臨時變量
5. Code
6. Logs
> Data location can only be specified for `array`, `struct` or `mapping` types
> `string` type actually is a `bytes` type
### Mappings
A mapping is a data structure where a key is "mapped" to a single value.
```sol
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.7;
// Contract: 0xd9145CCE52D386f254917e481eB44e9943F39138
contract SimpleStorage {
uint256 public favoriteNumber;
mapping(string => uint256) public nameToFavoriteNumber;
// Add `people` function
function addPerson(string memory _name, uint256 _favoriteNumber) public {
nameToFavoriteNumber[_name] = _favoriteNumber;
}
}
```
