ios - 检查 Firestore 查询 (whereField isEqualTo) 是否未找到任何文档

Question

我想检查我的 Firestore 查询是否找到了具有我想要的特定字段的任何文档。如果没有，我想继续编写其他代码。

不幸的是，我自己还没有找到解决这个问题的方法。你能帮忙吗？

代码:

Firestore.firestore().collection("conversations").whereField("mainUserID", isEqualTo: MainUID)
.whereField("otherUserID", isEqualTo: otherUserId).getDocuments { (snapshot, err) in
                
if snapshot.exists == true {                // Value of type 'QuerySnapshot?' has no member 'exists'
                        
                        
} else {
       
       }
}

Answer 1

来自文档

A FIRQueryDocumentSnapshot contains data read from a document in your Firestore database as part of a query. The document is guaranteed to exist and its data can be extracted with the data property or by using subscript syntax to access a specific field.

A FIRQueryDocumentSnapshot offers the same API surface as a FIRDocumentSnapshot. As deleted documents are not returned from queries, its exists property will always be true and data: will never return nil.

重要的是这个

The document is guaranteed to exist

因此，由于保证快照的存在，.exists 选项没有意义。

一种方法是检查快照中有多少文档

if docs.count > 0 {
   //there are docs
} else {
   //there are no docs
}