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//Creating a Mongo collection to keep track of events
EthEvents = new Mongo.Collection('ethEvents');
EthEvents.attachSchema(new SimpleSchema({
contractAddress: {
type: String,
index: true
},
eventName: {
type: String,
index: true
},
blockNumber: {
type: Number,
min: 0
}
}));
EthEvents.watchEvent = function (contractInstance, eventName, onEvent) {
if (!Contracts.useWeb3) {
return;
}
//What's the blocknumber of the event we've received before the restart?
var previous = EthEvents.findOne({
contractAddress: contractInstance.address,
eventName: eventName
});
//TODO handle forks
var fromBlock = previous ? previous.blockNumber + 1 : 0;
var options = {
'address': contractInstance.address,
'fromBlock': fromBlock
};
var updateFromBlock = function (err, event) {
//First update mongodb, then execute onEvent handler. Should mongo crash or fail, at least we re-receive the latest event
EthEvents.upsert({
contractAddress: contractInstance.address,
eventName: eventName
}, {
$set: {
blockNumber: event.blockNumber
}
}, function (dbError) {
if (!dbError) {
onEvent(err, event);
};
});
};
var contractEvent = contractInstance[eventName];
contractEvent({}, options).watch(Meteor.bindEnvironment(updateFromBlock));
console.log("init filter event", eventName, "of contract", contractInstance.address, "from block", fromBlock);
};
//TODO add proper error handling. Do something with success and failure returns in the Ethereum contracts also
EthEvents.handleCall = function (onSuccess) {
return Meteor.bindEnvironment(function (e, tx) {
if (!e) {
onSuccess(tx);
} else {
console.log("Failed to call Ethereum", e);
}
});
};
//You can watch events using the following code:
/*
EthEvents.watchEvent(MyContracABI, "<EventName>", myHandler);
MyContractABI is an contract instance, Eventname is of course the name of the even. MyHandler is a simple function with params (err, event) to handle the event.
*/
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