Estoy desarrollando un dapp usando 'testrpc' y 'truffle'-3.1.1. También he usado ethereum-bridge para Oraclize. He escrito una función de contrato inteligente que llama a una URL usando 'OraclizeQuery'.
El siguiente es el código del contrato: -
pragma solidity ^0.4.0;
import "./usingOraclize.sol";
contract WeatherApiCall is usingOraclize {
string public weathercondition;
event LOG_OraclizeCallback(
bytes32 queryId,
string result
);
function WeatherApiCall() {
OAR = OraclizeAddrResolverI(0x44bc501f0d92a9583877636828f52abc9da5d585);//OAR address
}
function __callback(bytes32 myid, string result) {
if (msg.sender != oraclize_cbAddress()) throw;
weathercondition=result;
LOG_OraclizeCallback(myid,result);
}
function update(string to,string datetime) payable returns(bool sufficient) {
oraclize_query("URL", strConcat("json(http://api.openweathermap.org/data/2.5/forecast?q='", to ,"'&mode=json&APPID=d2e8279188c8649c17540f798c9cc972).list[?(@.dt_txt='", datetime, "')].weather[0].main"));
return true;
}
}
El siguiente es el archivo index.html: -
<!DOCTYPE html>
<html>
<head>
<title>Sample Truffle App</title>
<link href='https://fonts.googleapis.com/css?family=Open+Sans:400,700' rel='stylesheet' type='text/css'>
<script src="./app.js"></script>
</head>
<body>
<h1>Airline</h1>
<h2>Example Truffle Dapp</h2>
<br>
<h1>Form</h1>
<br><label for="from">From:</label><input type="text" id="from" placeholder="--Residing Place--"></input>
<br><label for="to">To:</label><input type="text" id="to" placeholder="--Travelling Place--"></input>
<br><label for="persons">No. of Persons:</label><input type="text" id="persons" placeholder="--No. of Persons--"></input>
<br><label for="date">Travel Date:</label><input type="text" id="date" placeholder="--Date of travel yyyy-MM-dd--"></input>
<br><label for="time">Destination Time:</label><input type="text" id="time" placeholder="--HH:mm:ss--"></input>
<br><br><button id="send" onclick="App.sendRequest()">Generate Quote</button>
<br><br>
</body>
</html>
El siguiente es el archivo app.js.
// Import the page's CSS. Webpack will know what to do with it.
import "../stylesheets/app.css";
// Import libraries we need.
import { default as Web3} from 'web3';
import { default as contract } from 'truffle-contract'
// Import our contract artifacts and turn them into usable abstractions.
import weatherapicall_artifacts from '../../build/contracts/WeatherApiCall.json'
// WeatherApiCall is our usable abstraction, which we'll use through the code below.
var WeatherApiCall = contract(weatherapicall_artifacts);
// The following code is simple to show off interacting with your contracts.
// As your needs grow you will likely need to change its form and structure.
// For application bootstrapping, check out window.addEventListener below.
var accounts;
var account;
window.App = {
start: function() {
var self = this;
// Bootstrap the WeatherApiCall abstraction for Use.
WeatherApiCall.setProvider(web3.currentProvider);
// Get the initial account balance so it can be displayed.
web3.eth.getAccounts(function(err, accs) {
if (err != null) {
alert("There was an error fetching your accounts.");
return;
}
if (accs.length == 0) {
alert("Couldn't get any accounts! Make sure your Ethereum client is configured correctly.");
return;
}
accounts = accs;
account = accounts[0];
});
},
sendRequest: function() {
var queryRecheck = function(contract){
var bn = web3.eth.blockNumber; // returns the current block number
var logger = contract.LOG_OraclizeCallback(null, { fromBlock: bn });
console.log('Waiting on Oraclize queries...');
console.log(bn);
console.log(logger);
return new Promise(function (resolve, reject) {
var ctr = setInterval(function () {
logger.get(function (error, events) {
if (error)
reject(error);
try {
if (typeof events !== 'undefined') {
events.forEach(function (evt) {
if (evt.args.block.toNumber() > bn) {
clearInterval(ctr);
resolve();
}
});
}
} catch (e) {
console.log('Error encountered during query wait: ' + e);
reject(e);
}
});
}, 50000);
});
}
var self = this;
var fromdata = document.getElementById("from").value;
var to = document.getElementById("to").value;
var persons = parseInt(document.getElementById("persons").value);
var date = document.getElementById("date").value;
var time = document.getElementById("time").value;
//verifying at javascript console
console.log(fromdata);
console.log(to);
console.log(persons);
console.log(date);
console.log(time);
var timeperiod;
if ((time >= '00:00:00') && (time < '03:00:00')) {
timeperiod = '00:00:00';
} else if ((time >= '03:00:00') && (time < '06:00:00')) {
timeperiod = '03:00:00';
} else if ((time >= '06:00:00') && (time < '09:00:00')) {
timeperiod = '06:00:00';
} else if ((time >= '09:00:00') && (time < '12:00:00')) {
timeperiod = '09:00:00';
} else if ((time >= '12:00:00') && (time < '15:00:00')) {
timeperiod = '12:00:00';
} else if ((time >= '15:00:00') && (time < '18:00:00')) {
timeperiod = '15:00:00';
} else if ((time >= '18:00:00') && (time < '21:00:00')) {
timeperiod = '18:00:00';
} else if ((time >= '21:00:00') && (time < '24:00:00')) {
timeperiod = '21:00:00';
}
var datetime = date + ' ' + timeperiod;
console.log(datetime);
WeatherApiCall.deployed().then(function(instance) {
console.log("Initializing");
instance.update(to,datetime, {from: account, gas: 3000000, value: web3.toWei(1, 'ether')})
.then(function(v){
console.log(v);
console.log("Function Executed");
return queryRecheck(instance);
}).then(function(events) {
console.log(events);
});
}).then(function() {
console.log("Testing");
}).catch(function(e) {
console.log(e);
});
}
};
window.addEventListener('load', function() {
// Checking if Web3 has been injected by the browser (Mist/MetaMask)
if (typeof web3 !== 'undefined') {
console.warn("Using web3 detected from external source. If you find that your accounts don't appear or you have 0 MetaCoin, ensure you've configured that source properly. If using MetaMask, see the following link. Feel free to delete this warning. :) http://truffleframework.com/tutorials/truffle-and-metamask")
// Use Mist/MetaMask's provider
window.web3 = new Web3(web3.currentProvider);
} else {
console.warn("No web3 detected. Falling back to http://localhost:8545. You should remove this fallback when you deploy live, as it's inherently insecure. Consider switching to Metamask for development. More info here: http://truffleframework.com/tutorials/truffle-and-metamask");
// fallback - use your fallback strategy (local node / hosted node + in-dapp id mgmt / fail)
window.web3 = new Web3(new Web3.providers.HttpProvider("http://localhost:8545"));
}
App.start();
});
El siguiente es el resultado generado en la consola de javascript: -
"No web3 detected. Falling back to http://localhost:8545. You should remove this fallback when you deploy live, as it's inherently insecure. Consider switching to Metamask for development. More info here: http://truffleframework.com/tutorials/truffle-and-metamask" app.js:25575:5
india app.js:25520:4
chennai app.js:25521:4
2 app.js:25522:4
2017-03-02 app.js:25523:4
12:00 app.js:25524:4
2017-03-02 09:00:00 app.js:25544:4
Initializing app.js:25549:27
Testing app.js:25561:50
Object { tx: "0xcaf76e6444507c3fb48007c3e7307a8dc…", receipt: Object, logs: Array[0] } app.js:25552:41
Function Executed app.js:25553:41
Waiting on Oraclize queries... app.js:25486:8
15 app.js:25487:8
Object { requestManager: Object, options: Object, implementation: Object, filterId: null, callbacks: Array[0], getLogsCallbacks: Array[0], pollFilters: Array[0], formatter: bound () } app.js:25488:8
Error encountered during query wait: TypeError: evt.args.block is undefined app.js:25506:24
Error encountered during query wait: TypeError: evt.args.block is undefined app.js:25506:24
Error encountered during query wait: TypeError: evt.args.block is undefined app.js:25506:24
He intentado imprimir el resultado de Oraclize-Query en la consola de javascript... Pero devuelve el error... ¿Cómo se puede resolver?
Asegúrese de que su evento funcione según lo previsto y no esté vacío (agregue algunos console.log eventsantes de procesarlo). Como puede ver block, falta en el evtobjeto, probablemente porque su LOG_OraclizeCallbackevento ( https://github.com/Kottackal-ET-Practice/Flight-Dapp/blob/d5f6e5a661517e00ff37f48052b5e3a1afa8558d/contracts/WeatherApiCall.sol#L8-L13 ) no tiene blocken él, si está tratando de obtener el número de bloque del registro, puede acceder a él a través del blockNumberparámetro en el evtobjeto ( evt.blockNumber).