Convert FirestoreCollection into an array?

问题

I'm having difficulty converting the Firestore data into an array for the chart.js graph.

Getting the data from Firestore

fetchData(){

    //Get data
    this.updatesCollection = this.afs.collection(pathStats);

    this.updates = this.updatesCollection.valueChanges();
}

Creating the Chart

createChart(){

this.chart = new Chart('canvas', {
  type: 'line',
  data: {
    labels: ['5/18/18', '5/19/18', '5/20/18', '5/21/18', '5/22/18', '5/23/18'],
    datasets: [{
      label: 'Filled',
      backgroundColor: 'gray',
      data: [4, 3, 5, 2, 6, 7],
      fill: true,
    }]
  },
    }
)

I'm using the hard-coded values [4, 3, 5, 2, 6, 7] right now as a placeholder for my data points. How would I use the values coming from Firestore instead?

Solution

As mentioned by Ohad below:

let chartData;

this.updatesCollection.ref.get().then((querySnapshot) => {
    chartData = querySnapshot.docs.map(doc => doc.data());
}

This gets you an array with each document in it's own index. You can access individual properties like any other object (ie chartData[0].wheelCount).

回答1:

Calling this.updatesCollection.get() will asynchronously return a querySnapshot object.

A querySnapshot has a docs property which is an array containing zero or more documentSnapshot objects. The data in these can be extracted with the .data() method.

The code for producing your array could look like this:

let chartData = this.updates.collection.get()
  .then(querySnapshot => {
    chartData = querySnapshot.docs.map(doc => doc.data())
  })

来源：https://stackoverflow.com/questions/50519999/convert-firestorecollection-into-an-array