Question

我想知道是否可以在当前路径的完成块内访问另一条路径。

我使用它的方式如下......我有一个社交媒体应用程序，带有“帖子”路径。这显然是我获得帖子的所有信息的地方。我想为每个帖子创建“评论”。这就是我想要通往“评论”的途径。有人建议实现这一目标是什么？

Answer 1

以下是它应该如何工作的示例代码。在我的项目中使用相同的方法。当然，路径是假的，所以用你的实际路径填充它。

// Read all posts from Firebase
ref.child("posts").observeEventType(.Value, withBlock: { snapshot in

        if let snapshots = snapshot.children.allObjects as? [FIRDataSnapshot] {

            // Loop through all posts
            for snap in snapshots {

                // Read comments for each post. snap.key in code below represents post key. Don't know if you have same structure so fill your data here.
                ref.child("comment").child(snap.key).observeEventType(.Value, withBlock: { snapshot in
                    if let postDictionary = snapshot.value as? Dictionary<String, AnyObject> {

                        // Here you have comments for current post

                    }
                })
            }
        }
    })

Answer 2

I highly recommend first reading my classic answer on a similar question: Firebase data structure and url

Nesting data is in general discouraged in the Firebase Database. There have various reasons for that, but a few:

you can only retrieve a complete node. So if you nest the comments under each post, it means you will automatically get all comments whenever you are getting a post.
you often want different access rules on each of these types (posts vs comments). This is more difficult to manage when you nest them, since permission trickles down.

I would have three top-level lists: posts and comments.

posts
    $postid
        author: "uidOfCoderCody"
        title: "Firebase Data Retrieval, Path Inside Path" 
        body: "I would like to know if it possible to..."
comments
    $postid
        $commentid
            author: "uidOfZassX"
            comment: "Here is sample code of how it should work."

Since the comments are stored under the same $postid of the post itself, you can easily look up the comments for a post.

Depending on the use-cases that your app covers, you'll need to adapt or (more likely) expand this data model to efficiently allow your use-cases. For learning more, I also recommend reading this article on NoSQL data modeling.

Firebase数据检索，路径内部路径

2 个答案: