Query an array in Firebase SWIFT

Question

using swift and firebase I have a list of data like so

{
"posts" : {
 "-KHbULJcKqt9bSpxNO9k" : {
  "author" : "Michele",
  "postText" : "tags as arrays?",
  "tag" : [ "HELLO", "WHAT'S UP?", "TEST" ]
}

with many more post. I want to search by tag and if a post contains the search term as a tag return the whole post. Ive been able to do this with strings using queryEqualToValue: but haven't been able to solve it for an array. Any point in the right direction is appreciated thank you.

This is what my save function looks like

func createNewPost(post: Dictionary<String, AnyObject>, tags: [String]) {
    let firebaseNewPost = POST_REF.childByAutoId()
    let firebaseTag = Firebase(url: "\(POST_REF)/\(firebaseNewPost.key)/tag")

    print(firebaseTag)


    firebaseNewPost.setValue(post)

    for tag in tags {
        let tagID = firebaseTag.childByAutoId()

        tagID.setValue(tag)
    }
}

Now I need help with searching through the data and retrieving certain post based on what a user searches for. This is what I was using when it was just one tag and it was a just a string.

    func loadTaggedShit(searchTerm: String) {

    DataService.dataService.POST_REF.queryOrderedByChild("tag").queryEqualToValue(seachTerm).observeEventType(.ChildAdded, withBlock: { snapshot in
        self.posts = []

        if let snapshots = snapshot.children.allObjects as? [FDataSnapshot] {
            for snap in snapshots {
                if let postDictionary = snap.value as? Dictionary<String, AnyObject> {
                    let key = snap.key
                    let post = Post(key: key, dictionary: postDictionary)

                    self.posts.insert(post, atIndex: 0)
                }
            }
        }

        self.tableView.reloadData()


    })

}

also the data now looks like this

"posts":{
 "-KHj_bDJmZJut7knKoUX" : {
  "author" : "Michele",
  "postText" : "what's up",
  "tag" : {
    "-KHj_bDJmZJut7knKoUY" : "HEY"
   }
 }
}

Jay · Accepted Answer · 2018-08-26 13:18:02Z

1

Firebase arrays are very situational and really should be avoided if possible.

Array's in code are very powerful data constructs but they just don't work well within a JSON structure. If they are modified, say, removing a node, that index will be removed as well. That leaves the array with 'holes' e.g. 0, 1, 2, 4, 5, 7 etc. So, create yourself a tags child node within your post node, and then child nodes with keys created with childByAutoId

"posts" : {
 "-KHbULJcKqt9bSpxNO9k" : {
    "author" : "Michele",
    "postText" : "tags as arrays?",
    "tags"
       tag_id_0
         tag_title: "HELLO"
       tag_id_1
         tag_title: "WHAT'S UP?"
       tag_id_2
         tag_title: "TEST"
}

You might even consider creating a separate tags node and reference it within the posts node - especially if they are going to be re-usable.

Edit:

Based on some additional information, a different structure will be in order because the OP needs to query for posts that contain a specific tag and the tags are in fact reusable and not specific to a post:

posts
  -KHbULJcKqt9bSpxNO9k
    author: "Michele"
    postText: "tags as arrays?"
    tags
      tag_id_1: true
      tag_id_2: true
  -JPHJSojo91920LLK0J
    author: "Larry"
    postText: "NO, don't use arrays"
    tags
     tag_id_2: true

tags
  tag_id_0
    tag_title: "HELLO"
  tag_id_1
    tag_title: "WHAT'S UP?"
  tag_id_2
    tag_title: "TEST"

And then the code to receive all posts that use the TEST tag, tag_id_2

This is called a Firebase Deep Query

postsRef.queryOrderedByChild("tags/tag_id_2").queryEqualToValue(true)
        .observeSingleEventOfType(.Value, withBlock: { snapshot in
    print(snapshot)
})

edited Aug 26, 2018 at 13:18

answered May 13, 2016 at 18:16

Jay

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12 Comments

MicheleRuocco Over a year ago

Thank you Jay the post are not going to be modified once the user has posted it so would that change how you would do this?

Jay Over a year ago

@Michi314 If they are specific to the post and will not be changed then use the Firebase structure I posted. That way they are query-able, loadable and are easy to work with in general

MicheleRuocco Over a year ago

how would you go about saving the tags I tried but got the error no firebase namespace specified. This is the function that I made func createNewPost(post: Dictionary<String, AnyObject>, tags: [String]) { let firebaseNewPost = POST_REF.childByAutoId() let firebaseTag = Firebase(url: "(firebaseNewPost.key)/tags") firebaseNewPost.setValue(post) for tag in tags { let tagID = firebaseTag.childByAutoId() tagID.setValue(tag) } }

Jay Over a year ago

@Michi314 It's best practice to not post code in comments. The tag_is_0, tag_id_1 etc are nodes created with childByAutoId if that helps. Can you update your original question with your followup question?

MicheleRuocco Over a year ago

sorry about that I just figured it out but i'll update it with my new code could you also help with querying the data and finding specific post? Thank you

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