Question

8.7. 变量

			
address public minter;
string name;
int num;	

    uint constant x = 32**22 + 8;
    string constant text = "abc";
    bytes32 constant myHash = keccak256("abc");
    
    uint256 ticket = 1 ether;
			
		

变量赋值

			
pragma solidity ^0.4.25;

contract C {
    uint[] data;

    function f() public view returns (uint, bool, uint) {
        return (7, true, 2);
    }

    function g() public {
        // 声明和分配变量。 明确指定类型是不可能的。
        var (x, b, y) = f();
        // 分配给一个预先存在的变量。
        (x, y) = (2, 7);
        // 互换值的常用技巧对于非价值存储类型不起作用。
        (x, y) = (y, x);
        // 组件可以省略（也可以用于变量声明）。
        // 如果元组以空组件结束，其余的值将被丢弃。
        (data.length,) = f(); // 设置长度为 7
        // 在左边也可以做同样的事情。
        (,data[3]) = f(); // Sets data[3] to 2
        // 组件只能在作业的左侧排除，但有一个例外：
        (x,) = (1,);
        // (1,) 是指定1元组元的唯一方法，因为（1）等于1。
    }
}			
			
		

8.7.1. 全局变量

			
block.blockhash(uint blockNumber) returns (bytes32): hash of the given block - only
works for 256 most recent blocks
block.coinbase (address): current block miner’s address
block.difficulty (uint): current block difficulty
block.gaslimit (uint): current block gaslimit
block.number (uint): current block number
block.timestamp (uint): current block timestamp
msg.data (bytes): complete calldata
msg.gas (uint): remaining gas
msg.sender (address): sender of the message (current call)
msg.value (uint): number of wei sent with the message
now (uint): current block timestamp (alias for block.timestamp)
tx.gasprice (uint): gas price of the transaction
6.4. Solidity in Depth 99Solidity Documentation, 0.4.10
tx.origin (address): sender of the transaction (full call chain)
revert(): abort execution and revert state changes
keccak256(...) returns (bytes32): compute the Ethereum-SHA-3 (Keccak-256) hash of the
(tightly packed) arguments
sha3(...) returns (bytes32): an alias to keccak256()
sha256(...) returns (bytes32): compute the SHA-256 hash of the (tightly packed) arguments
ripemd160(...) returns (bytes20): compute the RIPEMD-160 hash of the (tightly packed) arguments
ecrecover(bytes32 hash, uint8 v, bytes32 r, bytes32 s) returns (address):
recover address associated with the public key from elliptic curve signature, return zero on error
addmod(uint x, uint y, uint k) returns (uint): compute (x + y) % k where the addition is performed with arbitrary precision and does not wrap around at 2**256
mulmod(uint x, uint y, uint k) returns (uint): compute (x * y) % k where the multiplication is performed with arbitrary precision and does not wrap around at 2**256
this (current contract’s type): the current contract, explicitly convertible to address
super: the contract one level higher in the inheritance hierarchy
selfdestruct(address recipient): destroy the current contract, sending its funds to the given address
.balance (uint256): balance of the Address in Wei
.send(uint256 amount) returns (bool): send given amount of Wei to Address, returns false on failure
.transfer(uint256 amount): send given amount of Wei to Address, throws on failure			
			
			

block.blockhash(uint blockNumber) returns (bytes32): 某个区块的区块链hash值
block.coinbase (address): 当前区块的挖矿地址
block.difficulty (uint): 当前区块的难度
block.gaslimit (uint): 当前区块的gaslimit
block.number (uint): 当前区块编号
block.timestamp (uint): 当前区块时间戳
msg.data (bytes): 参数数据
msg.gas (uint): 剩余的gas
msg.sender (address): 当前发送消息的地址，执行合约的地址。
msg.sig (bytes4): 方法ID
msg.value (uint): 执行合约时，转账的eth数量，以wei为单位。
now (uint): 时间戳，等价于block.timestamp (uint)
tx.gasprice (uint): 交易的gas单价
tx.origin (address):交易发送地址

8.7.2. storage

使用 storage 这个关键字时，当前的函数必须是internal或者private类型。

8.7.3. memory