2.Varibale

Varibale分两类：

• Primitive Data Types: 值类型传值时会将值拷贝一份，传递的是值本身，对其修改时并不会对原来值有影响。
• 始终按值来传递，当被用作函数参数或者用在赋值语句中时，总会进行值拷贝。
• 值类型里有两个比较特殊的类型是函数和地址（包括合约），会分为单独的部分介绍。
• 引用类型: 引用类型进行传递时，传递的是其指针，而引用类型进行传递时可以为值传递，也可以为引用传递。

值类型

• bool
• uint/int
• bytes
• address
• mapping
• enum
• struct
• bytes/String
• fixed

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.1;

contract ValueTypes {
    bool public b1 = true;

    /*
    unsign: 非负数
    unint 默认unit256     0-2^256
    unint8                0-2^8
    unint16               0-2^16 
*/
    uint256 public u = 123;

    /*
    想用负数怎么办，int
    int默认256       -2^255-2^255
    int128           -2^127-2^127
    */
    int256 public i = -123;
    int256 public minInt = type(int256).min;
    int256 public maxInt = type(int256).max;

    address public addr = 0xCA35b7d915458EF540aDe6068dFe2F44E8fa733c;

    /*
    byte 表示a sequence of byte 
    表示形式有两种：
        1. 大小固定的 byte array
        2. 大小动态变化的 byte arrays
    */
    bytes1 a = 0xb5; //  [10110101]
    bytes1 b = 0x56; //  [01010110]

    // Default values
    // Unassigned variables have a default value
    bool public defaultBoo; // false
    uint256 public defaultUint; // 0
    int256 public defaultInt; // 0
    address public defaultAddr; // 0x0000000000000000000000000000000000000000
}

默认值

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.1;

contract DefaultValues {
    bool public b;// false
    uint public u;// 0
    int public i;// 0
    address public a;//  0x0000000000000000000000000000000000000000
    bytes32 public b32;//  
    // mapping, structs, enums, fixed sized arrays 
}

更多

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.1;

contract Primitives {
    bool public boo = true;

    /*
    uint stands for unsigned integer, meaning non negative integers
    different sizes are available
        uint8   ranges from 0 to 2 ** 8 - 1
        uint16  ranges from 0 to 2 ** 16 - 1
        ...
        uint256 ranges from 0 to 2 ** 256 - 1
    */
    uint8 public u8 = 1;
    uint public u256 = 456;
    uint public u = 123; // uint is an alias for uint256

    /*
    Negative numbers are allowed for int types.
    Like uint, different ranges are available from int8 to int256

    int256 ranges from -2 ** 255 to 2 ** 255 - 1
    int128 ranges from -2 ** 127 to 2 ** 127 - 1
    */
    int8 public i8 = -1;
    int public i256 = 456;
    int public i = -123; // int is same as int256

    // minimum and maximum of int
    int public minInt = type(int).min;
    int public maxInt = type(int).max;

    address public addr = 0xCA35b7d915458EF540aDe6068dFe2F44E8fa733c;

    /*
    In Solidity, the data type byte represent a sequence of bytes. 
    Solidity presents two type of bytes types :

     - fixed-sized byte arrays
     - dynamically-sized byte arrays.

     The term bytes in Solidity represents a dynamic array of bytes. 
     It’s a shorthand for byte[] .
    */
    bytes1 a = 0xb5; //  [10110101]
    bytes1 b = 0x56; //  [01010110]

    // Default values
    // Unassigned variables have a default value
    bool public defaultBoo; // false
    uint public defaultUint; // 0
    int public defaultInt; // 0
    address public defaultAddr; // 0x0000000000000000000000000000000000000000
}

引用类型

Solidity 中，有一些数据类型由值类型组合而成，相比于简单的值类型，这些类型通常通过名称引用，被称为引用类型。

• array
• string: 是一个动态尺寸的 utf-8 编码字符串
• bytes: 动态十六进制字节数组
• mapping
• struct