4.3.1 使用remix调用合约获取data

    在使用remix执行合约方法时，每次交易都有对应的交易详情，可以在控制台看到交易信息里的函数调用的input，以及对应的decodeInput和decodeOutput。
    input就是调用函数时向区块链环境发送的JSON里的data。对应开放平台，在使用合约调用时，传入的data可以直接使用remix的data。

    4.3.2 使用ethers.js实现编码和解码

    2. var ethers = require('ethers')
    4. var  abi = [
    5.     {
    6.         "constant": false,
    7.         "inputs": [
    8.             {
    9.                 "name": "_str",
    10.                 "type": "string"
    11.             }
    12.         ],
    13.         "name": "saySomething",
    14.         "outputs": [
    15.             {
    16.                 "name": "",
    17.                 "type": "string"
    18.             }
    19.         ],
    20.         "payable": false,
    21.         "stateMutability": "nonpayable",
    22.         "type": "function"
    23.     },
    24.         "inputs": [
    26.                 "name": "_owner",
    27.                 "type": "address"
    28.             }
    29.         ],
    30.         "payable": false,
    31.         "stateMutability": "nonpayable",
    32.         "type": "constructor"
    33.     },
    34.     {
    35.         "constant": true,
    36.         "inputs": [],
    37.         "name": "info",
    38.         "outputs": [
    39.             {
    40.                 "name": "",
    41.                 "type": "string"
    42.             }
    43.         ],
    44.         "payable": false,
    45.         "stateMutability": "view",
    46.         "type": "function"
    47.     },
    48.     {
    50.         "name": "owner",
    51.         "outputs": [
    52.             {
    53.                 "name": "",
    54.                 "type": "address"
    55.             }
    56.         ],
    57.         "payable": false,
    58.         "stateMutability": "view",
    59.         "type": "function"
    60.     }
    61. ];
    62. var interface = new ethers.Interface(abi)
    63. var abiInstance = interface.functions[abi[0].name] // abi[0]即saySomething function的abi
    64. return abiInstance.sighash // 0xfe6b3783

    获取函数参数编码data的方法：
    使用ethers.utils.ABICoder的encode方法，如

    1. 0xfe6b37830000000000000000000000000000000000000000000000000000000000000020000000000000000000000000000000000000000000000000000000000000000b48656c6c6f20576f726c64000000000000000000000000000000000000000000

    可对比上面使用remix调用方法时的input值，两者结果一致。

    1. var ethers = require('ethers')
    3. var outputTypes = ['string']
    4. var response = "0x0000000000000000000000000000000000000000000000000000000000000020000000000000000000000000000000000000000000000000000000000000000b48656c6c6f20576f726c64000000000000000000000000000000000000000000"
    6. var abiCoder = new ethers.utils.AbiCoder()
    7. abiCoder.decode(outputTypes, response)

    decode结果根据传入的outputTypes数组长度，解析对应的参数。