Created
March 14, 2018 13:51
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Getting count of brands
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categorySchema.find({}) | |
.exec() | |
.then(categories => { | |
// When you return a promise from a .then callback, the promise that gets returned from the original .then | |
// resolves when the inner promise that you return resolves | |
return Promise.all(categories.map(cat=> { | |
return brandSchema.find({category: cat._id}).count() | |
})); | |
}) | |
.then(counts => { | |
// so this resolves when the Promise.all above resolves | |
// counts is an array of numbers. I don't know what you want to do with them. | |
console.log('DONE'); | |
}); |
So what you're asking for is, to a certain extent, simply impossible. It's not that it's impossible to push the results to an array -- it's that it won't matter. You might as well just resolve with the array and then handle it in the callback. It will never be populated synchronously.
What you need is a little less elegant, but inherently no more complicated.
categorySchema.find({})
.exec()
.then(categories => {
// When you return a promise from a .then callback, the promise that gets returned from the original .then
// resolves when the inner promise that you return resolves
return Promise.all(categories.map(cat=> {
return brandSchema
.find({category: cat._id})
.count()
// transform the count into the object you want. cat is still in scope, so we can just use it
// generally, if you want state like categories to continue through asynchronous code, you need to have your Promises
// resolve with that state so you can access it later. You could use an array outside of the Promise logic, but that's inelegant
// and harder to work with
.then(count => {
return {
_id: cat._id,
title: cat.title,
count,
};
});
}));
})
.then(results => {
// These results are what you wanted in resultArray
console.log('DONE');
});
Okay thanks! I kinda have started to understand the concept of promises now 👍
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What i really want to do with the numbers is actually something like this:
categorySchema.find({})
.exec()
.then(categories => {
// When you return a promise from a .then callback, the promise that gets returned from the original .then
// resolves when the inner promise that you return resolves
return Promise.all(categories.map(cat=> {
// What i really want to do is return an object with the following properties:
return brandSchema.find({category: cat._id}).count()
.exec()
.then((count)=>{
// then once all results are pushed into the array I want to log "DONE" below.
})
.then(counts => {
// so this resolves when the Promise.all above resolves
// counts is an array of numbers. I don't know what you want to do with them.
console.log('DONE');
});