Angular's $q is a powerful tool for handling asynchronous operations, while

Question

Angular's $q is a powerful tool for handling asynchronous operations, while

I've been struggling for hours trying to figure out how $q works. I'm attempting to use it with a function from the google.maps API, but I just can't seem to grasp it on my own. Maybe I completely misunderstand $q. Can someone help me or provide some insight?

Here's a simple example of what I'm trying to accomplish:

var geocoder = new google.maps.Geocoder();
let promise1 = geocoder.geocode({address: "someAddress"});
let promise2 = geocoder.geocode({address: "someOtherAddress"});
$q.all([promise1, promise2]).then(data => { 
    console.log(data) 
});

//The output I'm getting is: [undefined, undefined], which is not what I expected.

Where am I making mistakes? Here's the original async method from the Google API that works fine.

var geocoder = new google.maps.Geocoder();
geocoder.geocode({address: "someAddress"}, function(response, status){
    if(status === 'ok')
        //Do what I need with the response
    else
        //Do something else
});

I want to work with multiple requests, not just one. So, I need to store all the responses (and wait for them as it's an async function) before proceeding. That's why I'm trying to use $q to achieve my goal.

PS: I know there are many discussions about $q, but even after hours of researching, I can't seem to find a solution. Please don't suggest googling it.

Thanks in advance for your help!

javascript angularjs google-maps asynchronous promise

Answer 1

Answer №1

.geocode does not return a Promise, it uses a callback mechanism and as you have discovered, it returns undefined.

If you want to create a geocode function that returns a Promise, you can do so by:

const geocodePromise = (geocoder, params) => new Promise((resolve, reject)  => {
    geocoder.geocode(params, function(response, status) {
        if (status == 'ok') resolve(response);
        else reject(status);
    });
});

var geocoder = new google.maps.Geocoder();
let promise1 = geocodePromise(geocoder, {address: "someAddress"});
let promise2 = geocodePromise(geocoder, {address: "someOtherAddress"});
$q.all([promise1, promise2]).then(data => { 
    console.log(data) 
});

Alternatively, you can define a `geocodeP` method on the `google.maps.Geocoder` object:

google.maps.Geocoder.geocodeP = function geocodeP(params) {
    return new Promise((resolve, reject) => {
        this.geocode(params, function(response, status) {
            if (status == 'ok') resolve(response);
            else reject(status);
        });
    });
};
var geocoder = new google.maps.Geocoder();
let promise1 = geocoder.geocodeP({address: "someAddress"});
let promise2 = geocoder.geocodeP({address: "someOtherAddress"});
$q.all([promise1, promise2]).then(data => { 
    console.log(data) 
});

Answer 2

.geocode does not return a Promise, it uses a callback mechanism and as you have discovered, it returns undefined.

If you want to create a geocode function that returns a Promise, you can do so by:

const geocodePromise = (geocoder, params) => new Promise((resolve, reject)  => {
    geocoder.geocode(params, function(response, status) {
        if (status == 'ok') resolve(response);
        else reject(status);
    });
});

var geocoder = new google.maps.Geocoder();
let promise1 = geocodePromise(geocoder, {address: "someAddress"});
let promise2 = geocodePromise(geocoder, {address: "someOtherAddress"});
$q.all([promise1, promise2]).then(data => { 
    console.log(data) 
});

Alternatively, you can define a `geocodeP` method on the `google.maps.Geocoder` object:

google.maps.Geocoder.geocodeP = function geocodeP(params) {
    return new Promise((resolve, reject) => {
        this.geocode(params, function(response, status) {
            if (status == 'ok') resolve(response);
            else reject(status);
        });
    });
};
var geocoder = new google.maps.Geocoder();
let promise1 = geocoder.geocodeP({address: "someAddress"});
let promise2 = geocoder.geocodeP({address: "someOtherAddress"});
$q.all([promise1, promise2]).then(data => { 
    console.log(data) 
});

Answer 3

Answer №2

Which node module are you utilizing? Is it google-maps-api?

geocoder.geocode({address: "someAddress"});

Does it return a promise, or should you try this:

geocoder.geocode({address: "someAddress"}).then(data => console.log(data));

If it returns undefined, then the issue may lie with the API itself.

If data is not undefined, then the problem is not caused by the geocoder.geocode() part.

You can explore this library Get states of tasks ran by bluebird.all().spread()

Regarding the "double thread" you mentioned, JavaScript does not support multithreading. More information can be found at Why doesn't JavaScript support multithreading?

Answer 4

Which node module are you utilizing? Is it google-maps-api?

geocoder.geocode({address: "someAddress"});

Does it return a promise, or should you try this:

geocoder.geocode({address: "someAddress"}).then(data => console.log(data));

If it returns undefined, then the issue may lie with the API itself.

If data is not undefined, then the problem is not caused by the geocoder.geocode() part.

You can explore this library Get states of tasks ran by bluebird.all().spread()

Regarding the "double thread" you mentioned, JavaScript does not support multithreading. More information can be found at Why doesn't JavaScript support multithreading?

Angular's $q is a powerful tool for handling asynchronous operations, while

Answer №1

Answer №2

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