CODEWITHSUNDEEP
iosswiftfirebase
yuin265
yuin265

Reputation: 103

Swift: how to retrieve data from firebase?

My structure in firebase is as follows:

app name
   user ID
      wins = 7
      losses = 8

and my code to read the wins child node

ref = Database.database().reference().child(passUserID)
ref?.child("wins").observe(.childAdded, with: { (snapshot) in

     //Convert the info of the data into a string variable
     let getData = snapshot.value as? String
          print(getData)
})

But it prints nothing.

Upvotes: 2

Views: 7047

Answers (2)

gwinyai
gwinyai

Reputation: 2580

To read data from Firebase you attach a listener to a path which is what creates a FIRDatabase reference. A FIRDatabaseReference represents a particular location in your Firebase Database where there is a key-value pair list of children. So in your case, you have created a Firebase reference to the key "wins" which only points to a value and not a key-value pair. Your reference was valid up to this point:

    ref = Database.database().reference().child(passUserID) 

    //did you mean FIRDatabase and not Database??

This FIRDatabaseReference points to the key passUserID which has a key-value pair list of children ["wins":"7"] and ["losses":"8"] (NOTE: a key is always a string). So from your FIRDatabase reference, you create your observer as follows and read the value of "wins":

   ref?.observe(.childAdded, with: { (snapshot) in

    //Convert the info of the data into a string variable
    if let getData = snapshot.value as? [String:Any] {

        print(getData)

        let wins = getData["wins"] as? String

        print("\(wins)")

    }

})

The Child added event will fire off once per existing piece of data, the snapshot value will be an individual record rather than the entire list like you would get with the value event. As more items come in, this event will fire off with each item. So if "losses" is the first record you might not get the value of "wins". Is this what you are trying to achieve? If what you really wanted to know is the value of "wins" at that particular location and to know if this value has ever changed you should use the .value observer as follows:

    ref?.observe(.value, with: { (snapshot) in

    //Convert the info of the data into a string variable
    if let getData = snapshot.value as? [String:Any] {

        let wins = getData["wins"] as? String

        print("\(wins)") //check the value of wins is correct

    }

})

Or if you just wanted to get the know the value of wins just once and you are not worried about knowing if there any changes to it, use the "observeSingleEvent" instead of "observe".

EDIT

I saw your image and now realize you might also have a problem with your reference. Your ref should actually be something like: 

    ref = FIRDatabase.database().reference().child("game-").child(passUserID)

You have obscured what "game" is but a valid reference to "wins" will include it.

SECOND EDIT

I will add the following so you can properly debug the problem. Use this pattern to observe the value and see if you get an error returned and what is says: 

        ref.observe(.value, with: { (snapshot) in

             print(snapshot)

        }, withCancel: { (error) in

            print(error.localizedDescription)

        })

Normally it will give you an error if you cannot access that Firebase location because of a database rule. It will also be a good idea to see if print(snapshot) returns anything as above.

Upvotes: 3

Anurag Sharma
Anurag Sharma

Reputation: 4824

You need this:

    ref.child("YOUR_TOP_MOST_KEY").observe(.childAdded, with: { (snapshot) in
        let keySnapshot = snapshot.key
        //print(keySnapshot)
        self.ref.child(keySnapshot).observe(.value, with: { (snapshot2) in
        //print(snapshot2)
        }) { (error) in
            print("error###\(error)")

        }

    })

Upvotes: 0

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