Learn Solidity 5 Global Variables in Solidity

• 全局变量有很多，这里只讨论一些常用的，全部可以参考官方文档

• 中文文档

• 两个合约交互的例子，使用公共的变量msg.sender

// SPDX-License-Identifier: MIT
pragma solidity >= 0.7.0 < 0.9.0;

contract LedgerBalance {
    mapping(address => uint) balance;
    function updatesBalance(uint newBalance) public {
        balance[msg.sender] = newBalance;
    }
}

contract Updated {
    function updatesBalance() public {
        LedgerBalance ledgerBalance = new LedgerBalance();
        ledgerBalance.updatesBalance(30);
    }
}

• 一些其它的全局变量

// SPDX-License-Identifier: MIT
pragma solidity >= 0.7.0 < 0.9.0;

contract SimpleStorage {
    uint storedData;
    function set(uint x) public {
    //    storedData = x;
        // 区块难度
    //    storedData = block.difficulty;
    //    storedData = block.timestamp;
        storedData = block.number;
    }
    function get() public view returns (uint) {
        return storedData;
    }
}