Filter and sort on multiple values with Firebase

Question

I\'m building a social app using Firebase. I store posts in Firebase like this:

posts: {
   \"postid\": {
      author: \"userid\" 
      text: \"\",
      d         


        

Answer 1

You can use only one ordering function with Firebase database queries, but proper data structure will allow you to query by multiple fields.

In your case you want to order by category. Rather than have category as a property, it can act as an index under posts:

posts: {
   "categoryid": {
       "postid": {
         author: "userid" 
         text: "",
         date: "timestamp",
         category: "categoryid",
         likes: 23
       }
   }
}

Now you can write a query to get all the posts underneath a specific category.

let postsRef = Firebase(url: "<my-firebase-app>/posts")
let categoryId = "my-category"
let categoryRef = postsRef.childByAppendingPath(categoryId)
let query = categoryRef.queryOrderedByChild("date")
query.observeEventType(.ChildAdded) { (snap: FDataSnapshot!) {
  print(snap.value)
}

The code above creates a reference for posts by a specific category, and orders by the date. The multiple querying is possible by the data structure. The callback closure fires off for each individual item underneath the specified category.

If you want to query further, you'll have to do a client-side filtering of the data.