[英]How to get notified when an event triggers on ethereum smart contract
When someone makes a transfer from my account, an event gets trigger name 当有人从我的帐户转帐时,事件将获得触发名称
event Transfer(address indexed from, address indexed to, uint to)
Now I want to get notified when this event occurs on smart contract. 现在,我想在智能合约上发生此事件时得到通知。 I tried with difference things like filter, watch, subscription and etc. But nothing works as per need.
我尝试了一些不同的东西,例如过滤器,监视,订阅等。
I also have an another query What does filter, subscribe, and watch exactly do. 我还有另一个查询,“过滤”,“订阅”和“观看”到底是做什么的。 I am always getting confuse between these terms.
我总是对这些术语感到困惑。 Can someone give a clear idea.
有人可以给一个清晰的想法。
Note: I am using WEB3JS 1.0.0.26 version.
注意:我正在使用WEB3JS 1.0.0.26版本。
Here's a simple example for web3js 1.0.0.beta*
: 这是
web3js 1.0.0.beta*
的简单示例:
function handler (event) {
console.log(event.returnValues);
}
function errorCallback (err) {
console.error(err);
}
let subscription = contractObj.events.TestEvent().subscription;
subscription.on('data', handler).on('error', errorCallback);
To unsubscribe: 退订:
subscription.unsubscribe(function (result) {
console.log(result)
});
Example of usage in class: 在类中的用法示例:
class Listener {
constructor(event, handler) {
this.subscription = event;
this.subscription.on('data', handler).on('error', this.errorCallback);
}
errorCallback(err) {
console.log(err);
}
}
class Test {
constructor(contractObj) {
this.contractObj = contractObj;
this.createListener();
}
createListener() {
let self = this;
this.listener = new Listener(this.contractObj.events.TestEvent(), function (event) {
self.returnValues = event.returnValues;
});
}
}
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