javascript - 如何为 snapshotChanges lisitner 设置限制

Question

我正在使用 angular ngx admin，我只需要读取一个或 2 个，该怎么做？

this.firestore
  .collection(tablePages, (ref) =>
    ref
      .where("page.title", "==", pageName)
      .where("projectId", "==", localStorage.getItem("projectId"))
  )
  .snapshotChanges()
  .forEach((value) => {
    value.forEach((val) => {
      let p: MillaPage = val.payload.doc.data()["page"] as MillaPage;
      if (p != null) {
        p.id = val.payload.doc.id;

        this.mApp.pages.push(p);
      }
    });
  });

标签： javascriptfirebasegoogle-cloud-firestoreangularfire2

Answer 1

要限制从 Firestore 读取的文档数量，您可以对查询进行限制：

ref.where('page.title', '==', pageName)
   .where('projectId', '==', localStorage.getItem('projectId')
   .limit(2)