javascript - 在 ios ionic 应用程序中使用 javascript promise
<p><p>我需要在 ionic 中使用以下 promise (ios 显然在 android 上没问题):</p>
<pre><code>var Attendees = Parse.Object.extend("Attendees");
return Promise.all(eventDetails.map(detail => {
return Promise.all([new Promise((res, rej) => {
var query2 = new Parse.Query(Attendees);
query2.equalTo("event_id", detail .id_event);
query2.count({
success: function(number) {
detail["n_requests_received"] =number;
alert("received")
res('Some value if required'); //These are needed or promise chain will hang
}
});
}),
new Promise((res, rej) => {
var query3 = new Parse.Query(Attendees);
query3.equalTo("event_id", detail .id_event);
query3.equalTo("status", "confirmed")
query3.count({
success: function(number) {
detail["n_requests_confirmed"] =number;
// alert("confirmed")
res('Some value if required'); //These are needed or promise chain will hang
}
});
})]);
}));
</code></pre>
<p>你知道怎么做吗？</p></p>
<br><hr><h1><strong>Best Answer-推荐答案</ strong></h1><br>
<p><p>我使用 deferred 是为了让你可以运行一个 Promise 链，而不是将它们分开。如果调用发生错误，您还需要处理错误情况(两个 Promise 使用相同的错误函数)。它会正确地拒绝 promise ，以便您妥善处理。</p>
<pre><code>var promises = [];
eventDetails.forEach(function(detail) {
var deferred = $q.defer();
new Parse.Query('Attendees')
.equalTo("event_id", detail.id_event)
.count().then(function(number) {
detail["n_requests_received"] =number;
alert("received");
return new Parse.Query('Attendees')
.equalTo("event_id", detail .id_event)
.equalTo("status", "confirmed")
.count();
}).then(function(confirmedCount) {
detail["n_requests_confirmed"] = confirmedCount;
deferred.resolve('I have resolved this promise');
}, function(err) {
console.error(JSON.stringify(err));
deferred.reject('Error: ' + JSON.stringify(err));
});
promises.push(deferred.promise());
});
$q.all(promises).then(function(res) {
// completed all promises w/ no errors
}, function(err) {
console.error(JSON.stringify(err));
});
</code></pre></p>
<p style="font-size: 20px;">关于javascript - 在 iosionic 应用程序中使用 javascriptpromise ，我们在Stack Overflow上找到一个类似的问题：
<a href="https://stackoverflow.com/questions/38618329/" rel="noreferrer noopener nofollow" style="color: red;">
https://stackoverflow.com/questions/38618329/
</a>
</p>
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