[英]Angular js $asyncValidator “Undefined is not a function!” when passing promises
[英]Promises when passing a function as a parameter
我了解了Promise的大部分工作原理,但是當我需要將函數作為參數傳遞時,我很難理解如何處理它們:
var promise = new Promise(function(resolve, reject) {
// Do async job
ec2.describeInstances(function(err, data) {
console.log("\nIn describe instances:\n");
var list = [];
if (err) reject(err); // an error occurred
else {
var i = 0 ;
//console.log(data.Reservations);
var reservations = data.Reservations;
for (var i in reservations) {
var instances = reservations[i]['Instances'];
var j = 0;
//console.log(JSON.stringify(instances, null, 2));
for (j in instances){
var tags = instances[j]
var k = 0;
var instanceId = tags['InstanceId'];
var tag = tags['Tags'];
var l;
//console.log(tag);
for (l in tag){
//console.log(instanceId);
//console.log(tag[l]['Value']);
if (String(tag[l]['Value']) == '2018-10-15T23:45' || String(tag[l]['Key']) == 'killdate') {
console.log(tag[l]['Key'] + ' ' + tag[l]['Value']);
list.push(instanceId);
console.log(list);
//return(list);
}
}
}
}
resolve(list);
}
});
});
promise.then(function (list) {
ec2.terminateInstances(list, function(err, data) {
if (err) console.log(err, err.stack); // an error occurred
else console.log("made it"); });
});
在我將代碼的第一部分設為:
return new Promise(function(resolve, reject) { ... }
並在第一部分中起作用,但是當我將其更改為“ var”並在下面添加新的諾言后,它就停止了工作。 (編輯)我的意思是“停止工作”,這兩個函數均未運行,即:它在兩個函數中的任何一個完成之前都結束了處理程序,並且沒有return語句或控制台日志。
任何幫助將不勝感激!
謝謝!
想知道這樣的事情是否可行:
var promise = Promise.resolve(function() {
return ec2.describeInstances...
})
promise
.then(/* handle successful promise resolution */ )
.catch(/* handle promise rejection */ )
var promise = Promise.resolve();
promise
.then(function() {
return ec2.describeInstances(function(err, data) {
var list = [];
if (err) throw err; // an error occurred
// else logic
})
})
.catch(/* if needed here */)
.then(function (list) {
return ec2.terminateInstances(list, function(err, data) {
if (err) console.log(err, err.stack); // an error occurred
else console.log("made it"); });
})
.catch(/* if needed here */)
我的建議是破壞您的邏輯-處理您想要獲得的結果會更容易。
我認為正確的方法是:
承諾函數(服務函數):
function myAsyncFunction(url) {
return new Promise((resolve, reject) => {
result = () => resolve(data);
fail = () => reject(err);
});
}
然后您的答應者:
myAsyncFunction().then(dataHandler(result), // "promise worked!"
function (err) {// Error: "It broke"
console.log(err)
});
那么邏輯:
function dataHandler(data) { /* data logic */}
祝好運
我最終解決了它。 抱歉,在添加SNS部分之前忘了發回郵件。 我最終在此途中學習了大量有關函數式編程的知識,並決定在復雜的promise語法上使用await函數。 下面是代碼:
exports.handler = async (event, result, callback) => {
const AWS = require('aws-sdk');
const date = new Date().toISOString().substr(0, 16)
const ec2 = new AWS.EC2();
var sns = new AWS.SNS();
console.log("date is: " + date)
console.log(date.length);
const params = {
TopicArn:'arn:aws:sns:us-east-1:503782973686:test',
Message:'Success!!! ',
Subject: 'TestSNS'
}
const describeResult = await ec2.describeInstances().promise()
const terminatableInstances = await describeResult
.Reservations
.reduce((acc, reservation) => acc.concat(reservation.Instances), [])
//'2018-10-15T23:45'
.map((instance) => {
//console.log(instance)
//console.log(instance.Tags)
var date = instance.Tags
.filter(tag => tag.Key == 'killdate' && tag.Value == date) //date should be in this format on tag: 2018-10-15T23:45
.reduce((acc, curr) => curr.Value, null);
if (date != null) {
return instance.InstanceId;
}
return null;
})
.filter(id => id != null)
console.log(terminatableInstances);
const snsPush = await ec2.terminateInstances({
InstanceIds: terminatableInstances,
//DryRun: true //set this flag if you want to do a dry run without terming instances
}, (err, data) => {
if (err) {
console.log('no instances to terminate!')
}
else {
console.log('terminated instances')
}
})
console.log(snsPush)
//return(snsPush).promise()
return sns.publish(params, (err, data) => {
if (err) {
console.log(err, err.stack);
}
else {
console.log('sent');
}
}).promise();
};
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