I have a list component with a MatTableDataSource where I'm trying to wire it to a collection from AngularFireStore. I've followed a few tutorials where accessing the ,angular,firebase,angular-material"/>

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I have a list component with a MatTableDataSource where I'm trying to wire it to a collection from AngularFireStore. I've followed a few tutorials where accessing the

angular - Angular + Firebase：分配 Observable到 MatTableDataSouce

I have a list component with a MatTableDataSource where I'm trying to wire it to a collection from AngularFireStore. I've followed a few tutorials where accessing the

问题描述

I have a list component with a MatTableDataSource where I'm trying to wire it to a collection from AngularFireStore. I've followed a few tutorials where accessing the "payload" was in the component. I'm attempting to isolate the component from firebase specifcs in case I decide to change the backend later. I've broken my app.

Also, in general this code this works, but the error annoys me and the sorting and pagination are broken.

I get the following error:

Type 'Observable<Cart[]>' is missing the following properties from type 
'MatTableDataSource<Cart>':_data, _renderData, _filter, _internalPageChanges, and 18 more.

In the Cart Service, I have the following class defintion and constructor (the rest of the code is just CRUD stuff):

export class CartService {
  private cartCollection: AngularFirestoreCollection<Cart>;
  carts: Observable<Cart[]>;
  private cartDoc: AngularFirestoreDocument<Cart>;

  constructor(public db: AngularFirestore) {
    this.cartCollection = db.collection<Cart>('carts');
    this.carts = this.cartCollection.snapshotChanges().pipe(
      map(actions => actions.map(a => {
        const data = a.payload.doc.data() as Cart;
        const id = a.payload.doc.id;
        return { id, ...data };
      }))
    );
  }

....

In the Cart List component, I'm doing...

export class CartListComponent implements OnInit, AfterViewInit {
   public filteredCarts = new MatTableDataSource<Cart>();

...

then,

...
ngOnInit() {
  this.filteredCarts = this.service.carts; \\<- error lives here
}
...

How to get a value out of a dictionary

a = dict()
uid1 = 1
uid2 = 2
a[uid1] = {}
a[uid2] = {}
iid1 = 45
iid2 = 98
iid3 = 3
iid4 = 82
iid5 = 11
a[uid1][iid1] = 125
a[uid2][iid2] = 7
a[uid1][iid3] = 4
a[uid2][iid4] = 10
a[uid2][iid5] = 20

get a:

{1: {45: 125, 3: 4}, 2: {98: 7, 82: 10, 11: 20}}

What I want to get is to calculate the sum of 125+4=129 and 7+10+20=37

I've tried this:

for u,items in a.items():
    for i,counts in items.items():
        for count in counts:
            print(count)

got a notice like this:

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-48-8b6a2dace81e> in <module>
      1 for u,items in a.items():
      2     for i,counts in items.items():
----> 3         for count in counts:
      4             print(count)

TypeError: 'int' object is not iterable

Now I don't know how to proceed.

标签： angularfirebaseangular-material

解决方案

在@Powkachu 在他的评论中指出的方向：您正在混合数据类型，而且您可能没有订阅服务返回。尝试类似：

ngOnInit() {
    this.service.carts()
    .subscribe(res => {
      const data: Cart[] = res;
      this.filteredCarts = new MatTableDataSource<Cart>(data);
    });
  }

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