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How to wait for a bluebird promise to settle in multiple locations?

I have a situation where a bunch of functions are needing to wait for a promise to settle because it's the init function;

self.init=new Promise(function(resolve){
//do stuff, take awhile
resolve();
});


But, while it's init'ing, the async nature means other functions that depend on it being init are being called. I want those functions to wait for the init to finish, then continue.

I tried doing this inside each function

function doSomethingUseful(){
self.init.reflect().then(function () {
//do functions purpose
});
}
function doSomethingUseless(){
self.init.reflect().then(function () {
//do functions purpose
});
}


But it only works randomly, probably only works if init has settled, and if it hasn't, it just hangs here, weirdly hangs the whole app, despite it being async.

I am trying to replace a former solution that involved intervals and checking a Boolean isInit in each function call.

Is there a bluebird function to do this? Or another way to keep waiting and checking on a promise to see if it is resolved?

The app has this sort of structure in a number of places. Usually around sqlite read/writes. An init to open the database, but while it's opening, the page is loading and it's already trying to read/write to the tables, so those read/writes are forced to wait by using setInterval and repeatedly checking to see if the init has finished.

Here's an example using google analytics.

function Analytics() {
var self = this;
self.ready = ko.observable(false).subscribeTo('application:ready'); //attached to page ready event in jquerymobile and cordova
self.trackerInit = new Promise(function (resolve, reject) {
ko.computed(function () {
if (self.ready()) {
window.ga.startTrackerWithId('id', 1000, resolve, reject);
}
});
});
}

Analytics.prototype.trackSpeed = function (cat, interval, variable, label) {
var self = this;
console.log("speed tracker", cat, interval, variable, label); //this logs
return self.trackerInit.then(function () {
console.log("speed tracker confirm init"); //this never logs, all execution stops including other async code
return new Promise(function (resolve, reject) {
window.ga.trackTiming(cat, interval, variable, label, resolve, reject);
});
}).catch(function (e) {
if (e.message === "send timeout") {
return true; //who cares about timeouts anyways
} else {
throw e;//rethrow it
}
});
};


Function is called within page change event without a return, purely async. Calling it causes all execution to stop.

The ready ko is done like this

self.ready = ko.observable(false).publishOn('application:ready');

var deviceReady = new Promise(function (resolve) {
$(document).on('deviceready', resolve);
});
var pageReady = new Promise(function (resolve) {
$(document).on('pagecreate', resolve);
});

Promise.all([deviceReady, pageReady]).then(function () {
//a couple of page of code and...
self.ready(true);
});


Changing the init like this produces the same result of a hang when checking it's results

self.trackerInit = new Promise(function (resolve, reject) {
console.log("initting");
checker = setInterval(function () {
if (window.ga) {
console.log("ready init");
window.ga.startTrackerWithId('UA-23249898-11', 100, function(){
clearInterval(checker);
console.log("init complete");
resolve();
}, reject);
}
}, 1000);
});


isInit

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1 Answer
1

They are just promises. Just use then to chain them

then

function doSomethingUseful() {
// wait for init to finish, then do our stuff
// return the new chained promise in case someone wants to wait on us
return self.init.then(function () {
// do stuff
});
}

function doSomethingUseless() {
// wait for init to finish, then do our stuff
// return the new chained promise in case someone wants to wait on us
return self.init.then(function () {
// do stuff
});
}


// do both of those things and then do something else!
Promise.all([doSomethingUseful(), doSomethingUseless()]).then(function () {
console.log("init is done. And we've done something useful and useless.")
}


init

init

init

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