CODEWITHSUNDEEP
javascriptpromise
Filipe Ferminiano
Filipe Ferminiano

Reputation: 8791

Unable to handle promise failure inside other promise

I'm trying to use 2 promises, the second promise depends on the first one. And a 3 promise depends on both promises. But when first promise fails I get this error in the second promise:

UnhandledPromiseRejectionWarning: Unhandled promise rejection (rejection id: 2): TypeError: Cannot read property 'name' of null

This is my code:

var Asset  = require('../models/index').Asset;
var Price = require('../models/index').Price;

var currency = req.params.currency;

var values = { 
                where: { slugify_url: currency },                    
            };

// get asset information 
var promisse_asset = Asset.findOne(values); 


// get prices information on this asset
var promisse_prices = promisse_asset.then(function(asset) {

    console.log(asset); // outputs null
    // some processing
    if (!!asset) {
        ...  


});


return Promise.all([promisse_asset, promisse_prices]).then(function([asset, results]) {
    ...

How can I fix this? How can I handle when I don't find an Asset in my database?

Upvotes: 1

Views: 46

Answers (1)

HMR
HMR

Reputation: 39280

There is a situation where you want to batch process promises and get all the results including rejected ones with Promise.all. How you can do that is explained here (last code block).

There is a situation where you want to catch a rejecting promise on the queue and not on the stack without getting warnings (soon to be deprecated and getting errors). How you can do that is explained here.

Or you just wanted to reject a promise because the resolve value is not what you expected, you can throw as provided by Phil or return a Promise.reject("Something should not be null").

Upvotes: 1

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