Print All Children Columns from Firebase - iOS Swift 4

Question

I have 2 records in my users table

This code below

let fcmTokenRef = Database.database().reference().root.child("users").child(id!).child("fcmToken")
fcmTokenRef.observe(DataEventType.value, with: { (snapshot) in
    print(">>",snapshot)
})

will print out the token of a child

How do I adjust my code to print all the tokens for all my children?

excitedmicrobe · Answer 1 · 2018-12-07T19:15:59.290

1

You’re requesting a onetime read, hence you’re reading the data once. You need to use .childAdded

Try this:

let fcmTokenRef = Database.database().reference().child(“users”)
    fcmTokenRef.observe(.childAdded, with: { (snapshot) in
    print(">>",snapshot)
     guard let data = snapshot as? NSDictionary else {return}
     var each_token = data[“fcmToken”] as? String
     print(“all tokens: \(each_token!)”)
})

@puf says something very important: differences between child added and value firebase

The child_added event fires for each matching child under the node that you query. If there are no matching children, it will not fire.

edited Dec 07 '18 at 19:15

answered Dec 07 '18 at 17:00

excitedmicrobe

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@kyo isn’t needed, childAdded loops through every child in the collection. So nothing to worry – excitedmicrobe Dec 07 '18 at 17:02
If it is not why leave it as part of your answer ? can I remove it ? – code-8 Dec 07 '18 at 17:05
Also your suggested code seems malformed. See this error : https://i.imgur.com/EKfediu.png – code-8 Dec 07 '18 at 17:06
Updated, also update the curlies with the ones xcode suggest. Thanks – excitedmicrobe Dec 07 '18 at 17:08
I tried your code, it seems to compile fine, but when run in iPhone, it crash and showed me this error : https://i.imgur.com/vhwEWpz.png – code-8 Dec 07 '18 at 19:08
Thread 1: Fatal error: Unexpectedly found nil while unwrapping an Optional value – code-8 Dec 07 '18 at 19:08
Can you please elaborate ? Did I miss any part of your code ? – code-8 Dec 07 '18 at 19:09
@kyo updated, this time it should work with no errors at all – excitedmicrobe Dec 07 '18 at 19:16

Shehata Gamal · Accepted Answer · 2018-12-07T19:19:35.167

1

You can try

let fcmTokenRef = Database.database().reference().root.child("users").observe(DataEventType.value, with: { (snapshot) in 
      print(">>",snapshot)

      let dic = snapshot.value as! [String:[String:Any]]
      Array(dic.values).forEach { 
        let str = $0["fcmToken"] as! String
        print(str)
     }
})

edited Dec 07 '18 at 19:19

answered Dec 07 '18 at 17:02

Shehata Gamal

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for 1 observe replace `observe` with `observeSingleEvent` – Shehata Gamal Dec 07 '18 at 17:10
Your code compile fine, but stuck here when running on a phone. : https://i.imgur.com/LxtzS7C.png – code-8 Dec 07 '18 at 19:02
Can you please elaborate ? Did I miss any part of your code ? – code-8 Dec 07 '18 at 19:09
You updated code compiled perfect, and run perfectly on the phone. I got these on my console now . https://i.imgur.com/4PqScly.png – code-8 Dec 07 '18 at 19:10
What is `$0` mean ? – code-8 Dec 07 '18 at 19:12
it's like for loop item in `for item in arr` here `$0=item` – Shehata Gamal Dec 07 '18 at 19:13
What type is this `$0["fcmToken"]` ? Is there a way to find out ? – code-8 Dec 07 '18 at 19:17

Print All Children Columns from Firebase - iOS Swift 4

2 Answers2