本文节选自电子书《Netkiller Blockchain 手札》

Netkiller Blockchain 手札

本文作者最近在找工作，有意向致电 13113668890

Mr. Neo Chan, 陈景峯(BG7NYT)

中国广东省深圳市龙华新区民治街道溪山美地
518131
+86 13113668890

<netkiller@msn.com>

文档始创于2018-02-10

版权 © 2018 Netkiller(Neo Chan). All rights reserved.

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4.5. 数据类型

4.5.1. 数值型

int/uint：变长的有符号或无符号整型。变量支持的步长以8递增，支持从uint8到uint256，以及int8到int256。需要注意的是，uint和int默认代表的是uint256和int256。

有符号整型能够表示负数的代价是其能够存储正数的范围的缩小，因为其约一半的数值范围要用来表示负数。如：uint8的存储范围为0 ~ 255，而int8的范围为-127 ~ 127

支持的运算符:

比较：<=，<，==，!=，>=，>，返回值为bool类型。

位运算符：&，|，（^异或），（~非）。

数学运算：+，-，一元运算+，*，/，（%求余），（**次方），（<<左移），（>>右移）。
 

小数由"."组成，在他的左边或右边至少要包含一个数字。如"1."，".1"，"1.3"均是有效的小数。

4.5.1.1. 加 +，减 -，乘 *，除 ／ 运算演示

pragma solidity ^0.4.20; //Author: netkiller <netkiller@msn.com> //Home: http://www.netkiller.cn contract Math {    function mul(int a, int b) public pure returns (int) {        int c = a * b;       return c;   }    function div(int a, int b) public pure  returns (int) {        int c = a / b;       return c;   }    function sub(int a, int b) public pure  returns (int) {              return a - b;   }    function add(int a, int b) public pure  returns (int) {        int c = a + b;       return c;   } }

4.5.1.2. 求余 %

pragma solidity ^0.4.20; //Author: netkiller <netkiller@msn.com> //Home: http://www.netkiller.cn contract Math {    function m(int a, int b) public pure returns (int) {        int c = a % b;       return c;   } }

4.5.1.3. 幂运算

pragma solidity ^0.4.20; //Author: netkiller <netkiller@msn.com> //Home: http://www.netkiller.cn contract Math {    function m(uint a, uint b) public pure returns (uint) {        uint c = a**b;       return c;   }  }

4.5.1.4. 与 &，| 或，非 ～，^ 异或

pragma solidity ^0.4.20; //Author: netkiller <netkiller@msn.com> //Home: http://www.netkiller.cn contract Math {    function yu() public pure returns (uint) {        uint a = 3; // 0b0011       uint b = 4; // 0b0100            uint c = a & b; // 0b0000       return c; // 0   }    function huo() public pure returns (uint) {        uint a = 3; // 0b0011       uint b = 4; // 0b0100            uint c = a | b; // 0b0111       return c; // 7   }    function fei() public pure returns (uint8) {        uint8 a = 3; // 0b00000011       uint8 c = ~a; // 0b11111100       return c; // 0   }      function yihuo() public pure returns (uint) {        uint a = 3; // 0b0011       uint b = 4; // 0b0100            uint c = a ^ b; // 0b0111       return c; // 252   } }

4.5.1.5. 位移

pragma solidity ^0.4.20; //Author: netkiller <netkiller@msn.com> //Home: http://www.netkiller.cn  contract Math {    function leftShift() public pure returns (uint8) {        uint8 a = 8; // 0b00001000       uint8 c = a << 2; // 0b00100000       return c; // 32   }    function rightShift() public pure returns (uint8) {        uint8 a = 8; // 0b00001000       uint8 c = a >> 2; // 0b00000010       return c; // 2   }  }

a << n 表示a的二进制位向左移动n位，在保证位数没有溢出的情况下等价于 a乘以2的n次方。
a >> n 表示a的二进制位向右移动n位，在保证位数没有溢出的情况下等价于 a除以2的n次方。
 

4.5.2. 字符串

string 字符串类型，字符串可以通过""或者''来定义字符串的值

pragma solidity ^0.4.20; //Author: netkiller <netkiller@msn.com> //Home: http://www.netkiller.cn contract StringTest {      string name;          function StringTest() public{         name = "default";     }     function setName(string _name) public{         name = _name;     }     function getName() public view returns(string){         return name;     } }

4.5.2.1. 获取字符串长度

在 Solidity 中想获得字符串长度必须转成 bytes 类型然后使用 length 属性获得。bytes(string).length

pragma solidity ^0.4.20; //Author: netkiller <netkiller@msn.com> //Home: http://www.netkiller.cn contract StringTest {               string public name = "http://www.netkiller.cn";           function nameBytes() public constant returns (bytes) {                  return bytes(name);     }          function nameLength() public constant returns (uint) {                  return bytes(name).length;     }      function length(string _name) public pure returns (uint) {                  return bytes(_name).length;     }      }

	提示
注意：汉字采用UTF8编码，一个汉字等于3个字节，当你使用 length("景峯") 测试时会返回长度 6。

4.5.3. 布尔(Booleans)

bool: 可能的取值为常量值true和false。支持的运算符：

! 逻辑非  && 逻辑与  || 逻辑或  == 等于  != 不等于  bool a = true; bool b = !a;  // a == b -> false // a != b -> true // a || b -> true // a && b -> false

4.5.4. 字节类型

bytes names = "netkiller" bytes9 _names = "netkiller"; bytes(name)[0] = 0xFF;  bytes memory _tmp = new bytes(3); _tmp[0] = 0x4e; _tmp[1] = 0x65; _tmp[2] = 0x6f;

pragma solidity ^0.4.20; //Author: netkiller <netkiller@msn.com> //Home: http://www.netkiller.cn contract BytesTest {          bytes names = "netkiller";          function get() public view returns (bytes) {                  return names;     }     function getBytes2() public pure returns (bytes2) {         bytes9 _names = "netkiller";         return bytes2(_names);     }     function bytesToString() public constant returns (string) {                  return string(names);     }         function copyBytes(bytes b) public pure returns (bytes) {                bytes memory tmp = new bytes(b.length);                for(uint i = 0; i < b.length; i++) {                        tmp[i] = b[i];        }                return tmp;     }          function bytesToString2() public pure returns (string) {         bytes memory _tmp = new bytes(3);         _tmp[0] = 0x4e;         _tmp[1] = 0x65;         _tmp[2] = 0x6f;         return string(_tmp);     }     }

.length可以动态修改字节数组的长度

pragma solidity ^0.4.20; //Author: netkiller <netkiller@msn.com> //Home: http://www.netkiller.cn contract BytesTest2 {          // 初始化一个两个字节空间的字节数组     bytes public array = new bytes(2);          // 设置修改字节数组的长度     function setLength(uint _len) public {         array.length = _len;     }          // 返回字节数组的长度     function getLength() constant public returns (uint) {         return array.length;     }          // 往字节数组中添加字节     function pushArray(byte _tmp) public{         array.push(_tmp);     }      }

4.5.5. 数组

//创建一个memory的数组 	uint[] memory a = new uint[](7); 	 	uint[] x = [uint(1), 3, 4]; 	     bytes memory b = new bytes(10);

二维数组

uint [2][3] T = [[1,2],[3,4],[5,6]];

pragma solidity ^0.4.20; //Author: netkiller <netkiller@msn.com> //Home: http://www.netkiller.cn contract ArrayTest {          uint [] array = [1,2,3,4,5];          // 通过for循环计算数组内部的值的总和     function sum() constant public returns (uint) {         uint num = 0;         for(uint i = 0; i < array.length; i++) {             num = num + array[i];         }         return num;     }          function sumNumbers(uint[] _numbers) public pure returns (uint) {         uint num = 0;         for(uint i = 0; i < _numbers.length; i++) {             num = num + _numbers[i];         }         return num;     }      }

4.5.5.1. length

.length 属性是活动数组的尺寸

pragma solidity ^0.4.20; //Author: netkiller <netkiller@msn.com> //Home: http://www.netkiller.cn contract ArrayLength {          uint [] array = [1,2,3,4,5];          function getLength() public constant returns (uint) {                  return array.length;     }      }

4.5.5.2. push() 方法

通过 push 可以向数组中添加数据

pragma solidity ^0.4.20; //Author: netkiller <netkiller@msn.com> //Home: http://www.netkiller.cn contract ArrayLength {          uint [] array = [1,2,3,4,5];          function pushArray() public {                  array.push(6);     }          function getLength() public constant returns (uint) {                  return array.length;     }      }

4.5.6. 枚举类型

State 就是一个自定义的整型，当枚举数不够多时，它默认的类型为uint8，当枚举数足够多时，它会自动变成uint16，枚举下标定义从左至右从零开始。

New=0, Pending=1, Done=2, Deleted=3

访问枚举方式 State.New 实际等于数字 0

pragma solidity ^0.4.20; //Author: netkiller <netkiller@msn.com> //Home: http://www.netkiller.cn contract EnumTest {     enum State { New, Pending, Done, Deleted }     State state = State.New;      function set(State _state) public {         state = _state;     }      function get() constant public returns (State) {         return state;     }  }

枚举用来定义状态

pragma solidity ^0.4.0;  contract Purchase {     enum State { Created, Locked, Inactive } // Enum }

4.5.7. 结构体

定义结构体

struct Voter {         uint weight; // weight is accumulated by delegation         bool voted;  // if true, that person already voted         address delegate; // person delegated to         uint vote;   // index of the voted proposal     }      // This is a type for a single proposal.     struct Proposal {         bytes32 name;   // short name (up to 32 bytes)         uint voteCount; // number of accumulated votes     }

演示例子

pragma solidity ^0.4.20; //Author: netkiller <netkiller@msn.com> //Home: http://www.netkiller.cn contract Students {          struct Person {         string name;         uint age;         uint class;              }      Person person = Person("Neo",18,1);      function getPerson() public view returns(string){         return person.name;     } }

4.5.8. address

address public minter;

下面是一个获得账号余额的例子。

pragma solidity ^0.4.20; //Author: netkiller <netkiller@msn.com> //Home: http://www.netkiller.cn contract AddressTest{          function getBalance(address _addr) public constant returns (uint){         return _addr.balance;     }  }

4.5.8.1. payable

4.5.8.2. .value()

4.5.8.3. .gas()

4.5.9. mapping

mapping 就是图数据结构，由 key 和 value 组成。

pragma solidity ^0.4.20; //Author: netkiller <netkiller@msn.com> //Home: http://www.netkiller.cn contract MappingExample {          mapping(uint => string) map;      function put(uint key, string value) public {         map[key] = value;     }          function get(uint key) constant public returns (string) {         return map[key];     } }