Get a database reference in the new Firebase 4.0 release

问题

In Firebase 3.0+ the method to get the database reference was as such:

var ref: FIRDatabaseReference!

ref = FIRDatabase.database().reference()


ref.child("rooms").observeSingleEventOfType(.Value, withBlock: { (snapshot) in

    if snapshot.hasChild("room1"){

        print("true rooms exist")

    }else{

        print("false room doesn't exist")
    }

})

In Firebase 4.0 the naming convention changed but I can't get it to work!?

var ref: DatabaseReference!    
ref = Database.database().reference()

Has anyone else encountered this?

The swift compiler is suggesting removing the () from the lowercase database function call

if you remove it, it then throws the error message:

Database has no member reference

So how do you get the reference then!?

Pod file:

pod 'Firebase/Core'
pod 'Firebase/Database'

回答1:

The firebase documentation needs to be updated. 1. import both of these at the top of your class

import FirebaseCore

import FirebaseDatabase

Getting a DB reference only works within ViewDidLoad()

override func viewDidLoad() {

super.viewDidLoad()
var ref: DatabaseReference!
ref = Database.database().reference()
}

回答2:

You need to use the update code, perhaps the compiler hasn't done a good job of suggesting a fix

var ref: DatabaseReference!

ref = Database.database().reference()  

ref.child("rooms").observeSingleEvent(of: .value, with: { (snapshot) in

  // ...

  })

as you can see, the code works perfectly, consider pod deintegrate & pod update

回答3:

Your syntax seems right to me (for the new Firebase 4):

var ref: DatabaseReference!    
ref = Database.database().reference()

And, looking at their source code (FIRDatabase.h), everything you are doing matches perfectly:

FIR_SWIFT_NAME(Database)
@interface FIRDatabase : NSObject

+ (FIRDatabase *) database FIR_SWIFT_NAME(database());

- (FIRDatabaseReference *) reference;

Are you sure you are on their latest SDK version? As a last resort, try this:

pod cache clean
rm Podfile.lock
rm -rf Pods
pod install
rm -rf DerivedData

回答4:

For Firebase 4.0, there is a change

Removing the FIR prefix across names for all constants, protocols, classes, enums, and type definitions.
Renaming FIRApp to FirebaseApp.
Renaming FIROptions to FirebaseOptions.

Link: https://firebase.google.com/docs/reference/ios/naming-migration-guide

来源：https://stackoverflow.com/questions/44078673/get-a-database-reference-in-the-new-firebase-4-0-release

标签

ios

swift

firebase

firebase-realtime-database