Swift Firebase 数据库覆盖

Question

I am making a real-time messenger using Firebase. Currently, whenever I press a button I want a new message to be appended to the channel with the index of the message, but currently, whenever I press the button a new message is created that overwrites the old message. I know that setValue is usually the issue, but I really cannot tell what I'm doing wrong. What the database looks like before I add my new message . This is what it looks like after I add a new message here , and then the code I am using to add to the database.

@IBAction func sendMessageTapped(_ sender: Any) {
    if messageTextField.text == "" {
        print("blank")
        return
    } else {
        // First we will update the amount of messages that the channel has.
        ref.child("channels").child(channelName!).setValue(["numberOfMessages" : numberOfMessages+1 ])
        numberOfMessages += 1
        // after we have updated the amount of messages we will try to create a new message.
        ref.child("channels").child(channelName!).child("messages").child(String(numberOfMessages)).child("message").child("content").setValue(messageTextField.text)
        ref.child("channels").child(channelName!).child("messages").child(String(numberOfMessages)).child("message").child("name").setValue("Buddy")

    }
}

Answer 1

ok, Firebase is not a traditional table based database, is a DOCUMENT based database. At the very top you have a thing called a "collection" which is just a list of "document" things. In your case, you'd have several collection things to serve as channels: "General", "TopicQ", "InterstingStuff" etc, and within them each message as a document. No need to have a document, to then list the messages within it.

Second, you don't need indexes as you're using them, make the message id an attribute of the message, because firebase support querying by field, and even then is questionable because if you make each message a document, they will have their own auto generated id's if you want.

Third, in your code you're rewriting the whole document each time, this is why you lose your previous messages, so if you keep it, you need to add a merge option:

// Update one field, creating the document if it does not exist.
db.collection("cities").document("BJ").setData([ "capital": true ], merge: true)

Answer 2

you probably want to do something like this. This is what I did for my app, hope this helps someone. This rootRef.childByAutoId() generates a new entry with unique id. You can use this as reference for your case.

 let rootRef = Database.database().reference(withPath: "channels")
 let childRef = rootRef.childByAutoId()
 let values = ["Type": self.textField.text!, "message": self.textView.text!] as? [String : Any]
 childRef.updateChildValues(values)