Question

因此，如果我运行的查询未返回任何结果，则我尝试将文档添加到集合中。我将查询放在下面，但是没有运算符可用于检查结果查询的长度或大小。我该怎么办？

以下是查询：

this.monthCollection = this.afs.collection('users').doc(this.auth.getUserId()).collection('months', ref => {
  return ref.where('endTimestamp', '>=', moment().unix()).limit(1);
});

如果该查询未返回任何文档，那么我需要运行createNewMonth();以添加到months集合中。这是createNewMonth`方法

createNewMonth() {
    let date = new Date(), y = date.getFullYear(), m = date.getMonth();
    let firstDay = new Date(y, m, 1);
    let lastDay = new Date(y, m + 1, 0);

    let newMonth = {
      categories: [],
      endTimestamp: moment(lastDay).unix(),
      name: this.getMonthNameFromTimestamp(moment().unix()),
      startTimestamp: moment(firstDay).unix(),
      totalSpent: 0
    }
    return this.monthCollection.add(newMonth);
  }

如果我使用.then()还是需要在查询之外，是否可以在查询中执行此操作？

编辑：所以我找到了一种创建它的方法，但是它每次都会创建2，而不仅仅是一次。这是代码。

this.currentMonth = this.monthCollection.snapshotChanges().map(snapshot => {
      if (snapshot.length <= 0) {
        this.createNewMonth();   <---- here is what I added, it creates 2
      }

      return snapshot.map(doc => {
        const data = doc.payload.doc.data();
        data.id = doc.payload.doc.id;
        this.currentMonthId = doc.payload.doc.id;
        this.currentMonthTotalSpent = doc.payload.doc.data().totalSpent;

        this.expenseCollection = this.monthCollection.doc(doc.payload.doc.id).collection('expenses');
        this.expenses = this.expenseCollection.snapshotChanges().map(snapshot => {
          return snapshot.map(doc => {
            const data = doc.payload.doc.data();
            data.id = doc.payload.doc.id;
            return data;
          });
        });
        return data;
      });
    });

Answer 1

在运行.snapshotChanges()的angularfire2中，您可以检查是否找到了这样的结果：

this.dbRef.snapshotChanges().subscribe(doc => {

if(doc.payload.exists)
{
///Do something with the returned data
}
else
{
this.createNewMonth();
}

});

在查找.valueChanges()时，如果找不到数据，则'doc'将返回为null：

this.dbRef.valueChanges().subscribe(doc => {

if(doc)
{
///Do something with the returned data
}
else
{
this.createNewMonth();
}

});

如果查询返回0个文档，则添加文档

1 个答案: