web3.eth.contract

创建一个Solidity的合约对象，用来在某个地址上初始化合约。

调用：

web3.eth.contract(abiArray)

参数：

abiArray： Array - 一到多个描述合约的函数，事件的ABI对象。

返回值：

Object - 一个合约对象。

示例：

var MyContract = web3.eth.contract(abiArray);

// instantiate by address
var contractInstance = MyContract.at([address]);

// deploy new contract
var contractInstance = MyContract.new([contructorParam1] [, contructorParam2], {data: '0x12345...', from: myAccount, gas: 1000000});

// Get the data to deploy the contract manually
var contractData = MyContract.new.getData([contructorParam1] [, contructorParam2], {data: '0x12345...'});
// contractData = '0x12345643213456000000000023434234'

你可以或者使用一个在某个地址上已经存在的合约，或者使用编译后的字节码部署一个全新的的合约。

// Instantiate from an existing address:
var myContractInstance = MyContract.at(myContractAddress);


// Or deploy a new contract:

// Deploy the contract asyncronous from Solidity file:
...
const fs = require("fs");
const solc = require('solc')

let source = fs.readFileSync('nameContract.sol', 'utf8');
let compiledContract = solc.compile(source, 1);
let abi = compiledContract.contracts['nameContract'].interface;
let bytecode = compiledContract.contracts['nameContract'].bytecode;
let gasEstimate = web3.eth.estimateGas({data: bytecode});
let MyContract = web3.eth.contract(JSON.parse(abi));

var myContractReturned = MyContract.new(param1, param2, {
   from:mySenderAddress,
   data:bytecode,
   gas:gasEstimate}, function(err, myContract){
    if(!err) {
       // NOTE: The callback will fire twice!
       // Once the contract has the transactionHash property set and once its deployed on an address.

       // e.g. check tx hash on the first call (transaction send)
       if(!myContract.address) {
           console.log(myContract.transactionHash) // The hash of the transaction, which deploys the contract

       // check address on the second call (contract deployed)
       } else {
           console.log(myContract.address) // the contract address
       }

       // Note that the returned "myContractReturned" === "myContract",
       // so the returned "myContractReturned" object will also get the address set.
    }
  });

// Deploy contract syncronous: The address will be added as soon as the contract is mined.
// Additionally you can watch the transaction by using the "transactionHash" property
var myContractInstance = MyContract.new(param1, param2, {data: myContractCode, gas: 300000, from: mySenderAddress});
myContractInstance.transactionHash // The hash of the transaction, which created the contract
myContractInstance.address // undefined at start, but will be auto-filled later

示例：

// contract abi
var abi = [{
     name: 'myConstantMethod',
     type: 'function',
     constant: true,
     inputs: [{ name: 'a', type: 'string' }],
     outputs: [{name: 'd', type: 'string' }]
}, {
     name: 'myStateChangingMethod',
     type: 'function',
     constant: false,
     inputs: [{ name: 'a', type: 'string' }, { name: 'b', type: 'int' }],
     outputs: []
}, {
     name: 'myEvent',
     type: 'event',
     inputs: [{name: 'a', type: 'int', indexed: true},{name: 'b', type: 'bool', indexed: false}]
}];

// creation of contract object
var MyContract = web3.eth.contract(abi);

// initiate contract for an address
var myContractInstance = MyContract.at('0xc4abd0339eb8d57087278718986382264244252f');

// call constant function
var result = myContractInstance.myConstantMethod('myParam');
console.log(result) // '0x25434534534'

// send a transaction to a function
myContractInstance.myStateChangingMethod('someParam1', 23, {value: 200, gas: 2000});

// short hand style
web3.eth.contract(abi).at(address).myAwesomeMethod(...);

// create filter
var filter = myContractInstance.myEvent({a: 5}, function (error, result) {
  if (!error)
    console.log(result);
    /*
    {
        address: '0x8718986382264244252fc4abd0339eb8d5708727',
        topics: "0x12345678901234567890123456789012", "0x0000000000000000000000000000000000000000000000000000000000000005",
        data: "0x0000000000000000000000000000000000000000000000000000000000000001",
        ...
    }
    */
});

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