我如何在地图功能中等待未来？

Question

我的功能在下面，我把错误屏幕截图放在它下面。我尝试了很多东西，但找不到优雅和正确的方法来实现这一点。感谢您的帮助。

**It works**

Future<List<UserLike>> getUserLikedPosts() async {
        return userCollection
            .document(_currentUserId)
            .collection(collection_like)
            .limit(POST_LOAD_LIMIT)
            .getDocuments()
            .then(
          (snapshot) {
            if (snapshot == null) return null;
            return snapshot.documents
                .map((userImage) =>
                    UserLike.fromEntity(UserLikeEntity.fromSnapshot(userImage)))
                .toList();
          },
        );
      }



**It does not work**

Future<List<UserLike>> getUserLikedPosts() async {
    return userCollection
        .document(_currentUserId)
        .collection(collection_like)
        .limit(POST_LOAD_LIMIT)
        .getDocuments()
        .then(
      (snapshot) {
        if (snapshot == null) return null;
        return snapshot.documents.map((userImage) async {
          final postEntity =
              UserLike.fromEntity(UserLikeEntity.fromSnapshot(userImage));

          // NEED TO GET DOWNLOAD URL AND UPDATE MY OBJECT
          final downloadUrl = await FirebaseStorage.instance
              .ref()
              .child("user/${post.userId}/post/${post.file}")
              .getDownloadURL();

          return postEntity.copyWith(downloadUrl: downloadUrl);
        }).toList();
      },
    );
  }

Answer 1

我找到了解决方案，也许有人需要它。

 Future<List<UserLike>> getUserLikedPosts() async {
    return userCollection
        .document(_currentUserId)
        .collection(collection_like)
        .limit(POST_LOAD_LIMIT)
        .getDocuments()
        .then(
      (snapshot) async {
        if (snapshot == null) return null;
        return await Future.wait(snapshot.documents.map((userImage) async {
          final post = UserLike.fromEntity(UserLikeEntity.fromSnapshot(userImage));
          final url = await _storageRef.child("user/${post.userId}/post/${post.file}").getDownloadURL();
          return post.copyWith(downloadUrl: url);
        }).toList());
      },
    );
  }