如何从Firestore中获取特定数据并在Objective-C中进行更新

我必须从Firestore获取我的用户，然后我想更新我的图像，它是字符串。我被困在一个地方

这是我的密码：

FIRFirestore *defaultFirestore = [FIRFirestore firestore];
FIRCollectionReference *colRef = [defaultFirestore collectionWithPath:@"users"]; // to fetch my user profile 
[colRef queryWhereField:@"name" isEqualTo:currentUser.name];

[colRef getDocumentsWithCompletion:^(FIRQuerySnapshot *snapshot, NSError *error) {
        if (error != nil) {
          NSLog(@"Error getting documents: %@", error);
        } else {
          for (FIRDocumentSnapshot *document in snapshot.documents) {
              NSLog(@"%@", document.data); // my profile and after that I want to update the image
          // here I want to update the user image how can I do it ??

          }
        }
      }];

试试这个：

 FIRFirestore *defaultFirestore = [FIRFirestore firestore];

    FIRCollectionReference *colRef = [defaultFirestore collectionWithPath:@"users"];

    FIRQuery *query = [colRef queryWhereField:@"name" isEqualTo:@"SIDDHANT Nigam"];

    [query getDocumentsWithCompletion:^(FIRQuerySnapshot *snapshot, NSError *error) {

            if (error != nil) {

              NSLog(@"Error getting documents: %@", error);

            } else {

               FIRDocumentSnapshot *document = snapshot.documents.firstObject;

               [document.reference updateData:@{

                        @"imageurl": @""

               }];
            }

          }];

}